1,720,984 research outputs found
Gas chemical adsorption characterization of lanthanide hexafluoroacetylacetonates
No full textNewly-established adsorption enthalpy and entropy values of 12 lanthanide hexafluoroacetylacetonates, denoted Ln[hfac]4, along with the experimental and theoretical methodology used to obtain these values, are presented for the first time. The results of this work can be used in conjunction with theoretical modeling techniques to optimize a large-scale gas-phase separation experiment using isothermal chromatography. The results to date indicate average adsorption enthalpy and entropy values of the 12 Ln[hfac]4 complexes ranging from −33 to −139 kJ/mol K and −299 to −557 J/mol, respectively
An Assessment of Radiological Hazards from Gold Mine Tailings in the Province of Gauteng in South Africa
Full text linkRadiological hazards associated with exposure to Naturally Occurring Radionuclides Materials from gold mine tailings in the province of Gauteng in South Africa were evaluated. A comparison was made with soil samples from a control area. In this study, gamma spectroscopy was used to measure the activity concentrations of these radionuclides in 56 soil samples from the mine tailings and 10 soil samples from the control area. The average activity concentrations in Bq∙kg−1 for Uranium-238, Thorium-232, and Potassium-40 from the mine tailings were found to be 785.3 ± 13.7, 43.9 ± 1.0 and 427.0 ± 13.1, respectively. On the other hand, the average activity concentrations in Bq∙kg−1 for Uranium-238, Thorium-232, and Potassium-40 from the control area were found to be 17.0.1 ± 0.4, 22.2 ± 0.5 and 496.8 ± 15.2, respectively. Radiological hazard parameters calculated from these activity concentrations were higher than recommended safe limits. In particular, calculated average values for the external hazard (Hex) and the internal hazard (Hin) from the mine tailings were found to be 2.4 and 4.5. Both these values were higher than unity, posing a significant health risk to the population in the area
Health Risk Assessment of Heavy Metals in Soils from Witwatersrand Gold Mining Basin, South Africa
Full text linkThe study evaluates the health risk caused by heavy metals to the inhabitants of a gold mining area. In this study, 56 soil samples from five mine tailings and 17 from two mine villages were collected and analyzed for Asernic (As), Lead (Pb), Mercury (Hg), Cadmium (Cd), Chromium (Cr), Cobalt (Co), Nickel (Ni), Copper (Cu) and Zinc (Zn) using ICP-MS. Measured concentrations of these heavy metals were then used to calculate the health risk for adults and children. Their concentrations were such that Cr > Ni > As > Zn > Cu > Co > Pb > Hg > Cd, with As, Cr and Ni higher than permissible levels. For the adult population, the Hazard Index value for all pathways was found to be 2.13, making non-carcinogenic effects significant to the adult population. For children, the Hazard Index value was 43.80, a value >>1, which poses serious non-carcinogenic effect to children living in the gold mining area. The carcinogenic risk was found to be 1.7 × 10−4 implying that 1 person in every 5882 adults may be affected. In addition, for children, in every 2725 individuals, 1 child may be affected (3.67 × 10−4). These carcinogenic risk values were both higher than acceptable values
Chemical toxicity of surface-based drinking water sources due to natural uranium pollutant around Princess Gold Mine Environs in Roodepoort, South Africa
No full textThe activity level of natural uranium pollutant in surface-based water around Princess Gold Mine in Roodepoort, South Africa was measured using inductively coupled plasma mass spectrometry. The highest activity level of 6.39E+04 mBq/L is reported in the reddish brown ochre surface water from tailing (SWA-RB) close to the houses, whereas the lowest value of 1.92E+03 mBq/L is reported in the flowing surface water (SRWA-5) 1 km away from the dump. Along the path high values of 1.56E+04, 1.07E+04, 1.57E+04 and 8.46E+03 mBq/L were reported at SRWA-2, SRWA-3 and SRWA-4, respectively. The inhabitants living around the tailings use the surface water for daily consumption. Based on the annual limit guideline for drinking water recommended by World Health Organization (731 L/year), this study revealed that, the community around this vicinity receives 2.10 mSv as the highest annual collective effective dose due to 238U in the drinking surface water. The radiological-health risks of 238U in the water samples analysed revealed the highest cancer mortality and morbidity values of 2.40E+03 and 3.67E+03, respectively. The mean chemical toxicity risk for the natural uranium over the lifetime consumption is 5.31E+05 ?g/kg/day which shows that the main human risk may likely be due to the chemical toxicity of natural uranium
Transfer Rates of 238U and 232Th for E. globulus, A. mearnsii, H. filipendula and Hazardous Effects of the Usage of Medicinal Plants From Around Gold Mine Dump Environs
No full textMedicinal plant consumption can be a source of human exposure to radioactive elements such as 238U and 232Th, which can lead to internal radiation doses. The uptake of 238U and 232Th from soils to the leaf samples of three different medicinal plant species (Eucalyptus globulus, Acacia mearnsii and Hyparrhenia filipendula) from the purlieu of the Princess gold mine dump, an abandoned contaminated tailings storage site (TSS), located at longitude 27°55′00″E and latitude 26°09′30″S in Davidsonville (Roodepoort, west of Johannesburg, South Africa) was measured. This was done using ICP-MS spectrometry and substantial differences were observed in the soil-plant transfer factor (TF) values between these radionuclides. The plant species E. globulus exhibited the highest uptake of 238U, with an average TF of 3.97, while that of H. filipendula was 0.01 and the lowest TF of 0.15 × 10−2 was measured for A. mearnsii. However, in the case of 232Th, the highest average TF was observed for A. mearnsii (0.29), followed by E. globulus (0.10) and lowest was measured for H. filipendula (0.27 × 10−2). The ratio of TF average value i.e., 238U to 232Th in the soil-plant leaves was 38.05 for E. globulus, 0.01 for A. mearnsii and 4.38 for H. filipendula
Applying nuclear forensic signatures in response to a nuclear security event from a South African nuclear facility
Full text linkPhD (Science with Radiation Science), North-West University, Mahikeng CampusUranium ore concentrates, also known as yellowcake, are a critical component of the nuclear fuel cycle and the result of uranium mining and processing. Uranium ore concentrate s refers to a group of uranium chemical compounds that include U3O8, UO3, UO2, and UO4xH2O (where x = 2 or 4). The distributions of trace elements in uranium ore concentrates may be linked to the geologic conditions under which the parent uranium ore developed, and so are unique to each deposit type. These chemical signatures might subsequently be employed as a crucial tool in nuclear forensic examination. In this study, several samples of uranium ore concentrate and uranium ore samples have been analyzed for their trace elements, rare earth elements, morphology, and isotopic ratios. This project aimed to apply nuclear forensic signatures in responding to nuclear security events from a nuclear facility in SA. Uranium ore concentrates and uranium ore samples were analyzed using gamma detector, SEM/EDS, and inductively coupled plasma mass spectrometry. It was found that the activity ratio of 235U/238U for uranium ore concentrates samples ranged between 0.0271 ± 0.0016 and 0.0393 ± 0.0082 respectively, while the activity ratio of 235U/238U for uranium ore samples ranged from 0.0326 ± 0.0021 and 0.0391 ± 0.00037. The sample images of uranium ore concentrates showed similar characteristics, as both have pores between their grains. They both have a grape-like shape stacked together. Uranium ore concentrates consisted of agglomerates particles. These results showed a difference in particle shape and texture. The aggregates of fine particles are reasonably common in all the uranium ore concentrates samples and may have been produced during vapor condensation, nucleation and coagulation of particulates in the mine furnace. SEM/EDS results in uranium ore concentrate samples contained 60 70 % of uranium. The uranium ore samples studied displayed a fine texture. SEM/EDS in uranium ore samples showed the oxygen (O), aluminum (Al), sulfur (S), potassium (K), iron (Fe) impurities and uranium was not detected. Uranium ore concentrate and uranium ore samples could be differentiated by elemental and rare earth elements concentrations. The results showed that the elemental concentrations of the uranium ore concentrates samples might be used to differentiate them from one another. Impurity elements, Ca, K, Mg and Na were the most dominant elements in both uranium ore samples. The mean concentrations in U ore1 were in the order K > Mg > Na > Ca respectively, while the mean concentrations in U ore2 were in the order K > Mg > Ca > Na respectively. Therefore, the differences displayed by impurity elements were not only different in the concentrations of these elements but the shapes of the spectrum formed were also significantly
different. The C1-chondrite rare earth elements patterns of UOCblack showed fractionation of light rare earth elements and flat enriched heavy rare earth elements and a significant negative Eu anomaly. UOC CUP-2 showed depleted light rare earth elements and flat heavy rare earth elements. ADU rare earth elements pattern showed fractionation for all the elements. The uranium ore concentrates analyzed showed large variability in rare earth element patterns as well as Eu anomalies. Rare earth element patterns for both uranium ore samples showed enriched light rare earth elements and depletion of heavy rare earth elements. During early ore processing of the uranium ore studied in this work, rare earth element abundances and U isotopes did not fractionate. The CN-REE patterns difference for all samples demonstrate that the rare earth element signatures remain effective forensic indications despite in-situ leaching processes. The (234U)/ (238U) isotope ratios of uranium ore concentrate samples ranged between 0.169 ± 0.00936 and 4.810 ± 4.540, where the (235U)/ (238U) is between 0.00615 ± 0.00005309 and 0.348 ± 0.326. The (234U)/ (238U) as isotope ratios of the U ore1 and U ore2 samples ranged between (21.90 ± 4.08) x 10-5and (5.65 ± 1.17) x 10-5, where the (235U)/ (238U) is between 0.0289 ± 0.00496 and 0.00760 ± 0.00167 respectively. It was found that the results for the (235U)/ (238U) ratios showed large differences between the uranium ore concentrate and uranium ore samples. Similar to the (235U)/ (238U) ratios, there are a significant difference for the (234U)/ (238U) ratios of the uranium ore concentrate and uranium ore samples. The activity ratio of 234U/238U and 235U/238U of uranium ore concentrate and uranium ore samples was 10.144 and 0.047 respectively. Due to the natural abundance of 235U being used to derive its isotopic concentration from the observed isotopic concentration of 238U, the activity ratio for 235U/238U was equal to the continental average of 0.047 for all samples. The uranium ore concentrate and uranium ore samples showed that they could be differentiated from one another based on the study's findings. These results reported here demonstrate that they can be applied during nuclear forensic events.Doctora
Application of Electronic Personal Dosimeter in Thermo-Luminescence and Isotopic Ratio Dating of Limestone Using Uranium Series
Full text linkMSc (Applied Radiation Science), North-West University, Mafikeng Campus, 2017Application of e lectronic personal dosimeter in Thermo-Luminescence and isotopic ratio dating of limestone using uranium series has been examined in the dating of prehistoric activities in Gaborone area of Mogoditshane-Tsolamosese (Block 4) Botswana. isotopic ratio of the stable 206Pb to the parent nuclide 238U, was valuable to this research as it enabled the isotopic ratio technique to be applied for the study with better precision and accuracy. The aim of this research was to investigate the age of limestone existence by Thermo-Luminescence (TL) and isotopic ratio dating of limestone using uranium series measured by electronic personal dosimeter (EPD). This was achieved by quantifying the limestone sediments used in Gaborone at different topographic locations as affected by natural and human activities, and thus determining the effectiveness of Thermo-Luminescence and isotopic ratio methods on dating of limestone. From both Thermo-Luminescence and isotopic ratio methods, varying results were obtained with average limestone ages of 26 MY and 16 MY respectively for the Gaborone area of Mogoditshane-Tsolamosese. The results of this work revealed that the isotopic ratio technique is more reliable than EPD-TL for limestone dating, and thus the 207Pb/2°6Pb inverse
Concordia plot from [so plot gave a weighted mean age of the samples as 4308 + 1900/-770 MY, with an MSWD of0.51.Master
Applications of ICP-MS and isotopic techniques in resolving nuclear forensic signatures in cobalt processing
Full text linkMSc (Applied Radiation Science and Technology), North-West University, Mafikeng Campus, 2018"Abstract not copied"Master
Effectiveness of an ADAM10 inhibitor as a radio-sensitizer to improve the treatment of cervical cancer
Full text linkMSc (Applied Radiation Science and Technology), North-West University, Mahikeng CampusCervical cancer is the third most common type of cancer in women in developing countries with around 570 000 cases and 311 000 deaths recorded worldwide in 2018. In South Africa, over 90% of the cases are related to human papillomavirus (HPV) infection and annually, 5 743 new cases and 3 027 deaths are registered. Surgery, external beam therapy and chemotherapy are the standard treatments of cervical cancer, where combined therapy increases the survival rate of the patients. Though early stage cancer is curable, the median overall survival in cases of an advanced, recurrent disease is just over a year. Due to a lack of regular screening in developing countries, cervical cancer is often only detected at an advanced stage and therapy is not always available. Thus, there is an urgent need to improve current treatments and develop new strategies to treat cervical cancer. The goal of this dissertation was to determine the effectiveness of a disintegrin and metalloproteinase (ADAM10) inhibitor as a radiosensitizer for the treatment of cervical cancer. Inhibition of ADAM10 has been considered as a promising novel targeted cancer treatment strategy due to its role in the shedding off of a number of substrates that drive cancer progression. In addition, due to its role in the radiation response (RR) and Notch signaling pathway, blocking ADAM10 could enhance the effectiveness of radiation therapy (RT). In this dissertation, we successfully optimized the migration, apoptosis and invasion assay. Based on our results, we could conclude that the deregulation of ADAM10 activity by GI254023X (GI) had an effect on the migration of the Hela cells since it slowed down the gap closure. However, only one repeat was performed due to COVID 19 restriction. In contrast, no effect of GI on the invasion of the cervical cancer cells was seen. Results of the CSA assay were unclear and need to be repeated in the future to make a conclusion on the effect of GI on colony formation. Finally, a trend was seen to increase the apoptosis of Hela cells when control was compared to 2Gy+GI, which was not visible when control was compared with 2Gy only. However, when 2Gy was compared to 2Gy+GI, no significant differences were seen in living or apoptotic cells. Combined therapy of GI and RT had no increased inhibitory effects compared to single therapy in any of the
assays studied. Therefore, based on our results, we could not conclude that GI254023X functions as a radiosensitizer for cervical cancer.Master
Evaluating radiological impacts due to uranium mining in the Erongo Region, Namibia
Full text linkDSc (Science with Radiation Science), North-West University, Mahikeng CampusThe unambiguous and continuously increasing exposures of human beings to terrestrial radiations is highly attributed to naturally occurring radioactive materials in the environments. Background radiation had been increasing gradually due to mining and milling activities worldwide to acquire nuclear materials needed for a response to electrical demands globally. The most significant health effects associated with the continued exposure to NORMs are lung cancer and leukemia. The main aim of this study was to evaluate the radiological risks associated with naturally occurring radioactive materials from uranium mining activities to critical groups in Erongo Region, Namibia. The study analyzed the radiological emissions of gamma rays in soil samples using high-purity germanium detector and determined the elemental and radiological concentrations in dust and water using inductively coupled plasma-mass spectrometry Equipment. The target radionuclides were 238U, 226Ra, 232Th and 40K. The weighted mean values of activity concentrations with standard deviations measured for 238U, 226Ra, 232Th and 40K in soil samples using high-purity germanium detector ranged between 104.77±5.23 and 4610.29±50.57 Bq.kg-1, 42.22±0.73 and 4909.40±18.13 Bq.kg-1, 91.02±1.09 and 436.74±5.16 Bq.kg-1, and 683.06±12.88 and 2225.00±52.65 Bq.kg-1, respectively. All activity concentrations calculated were found to be significantly higher than the world averages levels of 35, 33, 45 and 420 Bq.kg-1, respectively reported by United Nations Scientific Committee on the Effects of Atomic Radiation. Khan river was the only section of study with low radioactivity level. Mean values with standard deviation only for absorbed dose , radium equivalent, annual effective dose, internal and external hazard indices were ranging between 135.89±2.58 to 2290.70±23.53 nGy.h-1, 253.45±2.03 to 5271.51±19.28 Bq.kg-1 and 0.83± to 14.05± mSv.y-1, 0.86±0.01 to 27.51±0.01 and 0.68±0.01 to 14.25±0.01, respectively. Gamma and alpha indices were calculated ranging from 0.93±0.01 to 17.69±0.07, and 0.21±0.01 to 24.55±0.09, respectively. The probability of cancer development in a biological body was estimated by a human health related hazard known as excess lifetime cancer risk. The calculated cancer risks were ranging from 2.92x10-3 to 4.99x10-2 for the soil samples, values which were significantly higher than both the world average (0.29x10-3) and limit (1.45x10-3) documented by United
Nations Scientific Committee on the Effects of Atomic Radiation and International Commission on Radiation Protection, respectively.
The elemental and activity concentrations for naturally occurring radioactive materials were also determined using inductively coupled plasma-mass spectrometry. The mean values in water from the tailings and boreholes were 17.18 and 3.17 Bq.l-1 for 238U, 1.72 and 0.024 Bq.l-1 for 232Th and 12.40 and 11.58 Bq.l-1 for 40K, respectively. These calculated radioactivity concentration values exceeded the drinking water quality guidelines levels recommended by World Health Organization for gross alpha screening and gross beta levels of 0.5 mBq.l-1 and 1.0 mBq.l-1, respectively.
The results show that both tailings and borehole water were unsuitable for human consumption and therefore, contact with edible food must be avoided by all means. For the dust from mine 2, the average activity concentrations were 80.94 Bq.l-1 for 238U, 673.12 Bq.l-1 for 232Th and 27.95 Bq.l-1 for 40K. The results had shown high transferrable probability of thorium radionuclide in the atmosphere than uranium and potassium nuclides. In dust, 232Th was recorded with significant high value of radioactivity concentration at 673.12 Bq.l-1, which was higher than the world average level of 45 Bq.kg-1, documented by United Nations Scientific Committee on the Effects of Atomic Radiations.
On excess life cancer risks, the RESRAD-OFFSITE model 4.0 was used with ICRP 107 based radionuclide transformations transfer factors and ICRP 60 external, inhalation and ingestion dose conversion factors to perform the analysis. The cancer morbidity risks modelled for naturally occurring radioactive materials in both mines’ samples had shown that 226Ra was the highest contributor. The RESRAD modelling was performed on water, plants, soil and atmospheric exposure pathways by external gamma, inhalations and ingestions and had shown risk factors in descending order as 226Ra ˃ 232Th ˃ 40K ˃ 238U. In RESRAD-OFFSITE model code, the total cancer morbidity risks were recorded with about 3 persons per 1 000 populations (3 x 10-3) by tailings soil (stockpiles) and surrounding soil samples of mine 1 less than 7 to 8 persons per 1 000 populations (7 x 10-3 – 8 x 10-3) by tailings (stockpiles) soil samples in mine 2 less than 7 to 9 persons per 1 000 populations (7 x 10-3 – 9 x 10-3) by uranium ore samples of mine 1 were at risks of
developing cancer. This could explicitly prove that the modelled cancer risks in the region were higher than the recommended level of 1 x 10-5 factor for a population and 1 x 10-3 for a subpopulation documented by the World Health Organization as well as the world average (0.29 x 10-3) documented by the United Nations Scientific Committee on the Effects of Atomic Radiation.Doctora
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