RESUMEN
This study assessed the gamma-ray shielding potential of clay, sand, gypsum and kaolin commonly used as a building material in Northwestern, Nigeria. The radiological status of the samples was first evaluated by determining the activity concentrations of 238U, 232Th and 40K using NaI (Tl) detector after which elemental composition and mass density were determined using Neutron Activation Analytical Technique. After which the mass attenuation coefficients (MAC), linear attenuation coefficients (LAC), half value layer (HVL), tenth value layer (TVL), and effective atomic number (Zeff) were determined experimentally and theoretically using standard point sources of 137Cs and 60Co photon peaks (0.662 and 1.332, 1.173) MeV and Py-MLBUF software. The activity concentrations were found to range from 51 to 59 Bq kg-1 with a mean value of 59 Bq kg-1 for 238U, 24 to 27 Bq kg-1 with a mean value of 29 Bq kg-1 for 232Th, and 219 to 247 Bq kg-1 with a mean value of 247 Bq kg-1 for 40K which were about within the world recommended values of 33, 45 and 420 Bq kg-1 respectively. The results of the elemental compositions show that Si, Al, K, Fe, and Ba in clay and sand samples have concentrations in the range of 36.83-78.48%, 1.92-26.05%, 6.33-21.96%, 2.39-19.09%, and 0.09-1.44%, respectively, while in kaolin and gypsum, results revealed that Si, Al, K, Fe, and Ca range between 0.34 and 65.52%, 1.14-35.82%, 0.00-12.12%, 0.00-5.77%, and 0.00-96.6%, respectively. However, the concentrations of other elements such as Mg, Ti, Mn, Zn, Na, and Ba varied significantly with the samples. The results showed that clay has an average density of 1.96 g/cm3, sand has 2.32 g/cm3, kaolin has 2.63 g/cm3, and gypsum has the highest density with a value of 2.66 g/cm3 compared to other samples. During the measurements, a thallium-activated sodium-iodide NaI (TI) detector was used. A narrow beam transmission geometry condition was adopted for the measurements to ensure minimal scattered radiation. Absorption and attenuation of gamma beams as a function of sample thickness against gamma energy generally exhibit an increasing gamma ray behaviour as the sample thickness increases from 1 to 3 cm. The results showed that the gypsum, kaolin, sand, and clay were capable of attenuating 63.5%, 61.5%, 58.4%, and 44.2 of gamma-ray photons of energy 0.662 MeV at 3 cm thickness %, respectively, and 40.6%, 32.9%, 30.6%, and 27.3% of gamma energy 1.332 MeV at 3 cm thickness, respectively. The results showed that MAC, LAC, and Zeff of all the samples decreased with an increase in photon energy, while those of HVL and TVL increased. The experimental results for all the gamma-ray shielding parameters were found to be in good agreement with the theoretical values obtained using Py-MLBUF. The results have shown that all the samples have similar photon attenuation behaviours; however, gypsum has the best shielding potential than kaolin and this is attributed due to its highest density value.
RESUMEN
BACKGROUND: Steroid Sensitive Nephrotic Syndrome (SSNS) follows a relapsing and remitting course in many of the cases. Time for initial response to corticosteroids has been identified as a prognostic factor in idiopathic nephrotic syndrome. OBJECTIVES: To determine the time to initial remission as well as the pattern of relapses among children with SSNS in Umuahia South East Nigeria. METHODS: Records of children with SSNS from July 2013 to June 2018 were reviewed for responses to corticosteroid and relapses in their first year. RESULTS: Twenty-four children with Idiopathic Nephrotic syndrome were followed up for one year. Male to female ratio was 3:1 of which fifteen (62.5%) responded to steroid and they were aged 2 to 9 years. Median time to remission was 14 days. Of the 15 steroid responsive patients, 11 (73.3%) were early responders while 4 (26.7%) were late responders. Six patients had at least one episode of relapse giving a relapse rate of 40.0%. Of these six, four (66.7%) were infrequent relapsers while 2 (33.3%) were frequent relapsers. Relapse rate was not significantly different across age groups (p = 0.622) and gender (p = 0.294). Presence of hypertension, haematuria and delayed time to remission did not significantly influence relapse. Acute respiratory infection was the most frequent trigger of relapse. CONCLUSION: More than two-thirds of children with NS in our centre experience early steroid response while less than one-third respond after 4 weeks of therapy. Less than half of the children experience a relapse in the first year of follow up.
