NRU :: Browsing by Author "Biira, Saphina"

Browsing by Author "Biira, Saphina"

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Amorphisation of boron carbide under gamma irradiation
(Pramana Journal of Physics, 2020) Mirzayev, Matlab N.; Demir, Ertugrul; Mammadov, Khagani F.; Sukratov, Vladimir A.; Jabarov, Sakin H.; Biira, Saphina; Asgerov, Elmar B.; Tugrul, A. Beril
Boron carbide (B4C) has been widely used in nuclear reactors and nuclear applications. In thiswork, the high-purity (99.9%) B4C samples were irradiated using a gamma source (60Co) with a dose rate (D) of 0.27 Gy/s at different gamma irradiation doses at room temperature. Phase and microstructural characterisation of B4C samples were carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results displayed some degradation of the diffraction peaks. The calculations reveal that 62% of B4C has changed into the amorphous phase when the irradiation dose is 194.4 kGy. Fourier transform infrared spectroscopy (FTIR) was used to explain chemical bonds and functional groups ofB4Csamples before and after gammairradiation. The results showed thatC– Cchemical bonds areweaker thanB–Cchemical bonds and tend to break under gammairradiation. Element mapping analysis for each gamma irradiation dose of B4C samples was performed using SEM patterns. The dynamics of the elements on the surface and chemical formula of all B4C samples were also determined after gamma irradiation.
Analysis of solar radiation in Uganda (a case study of Kasese, Jinja and Soroti Districts)
(International Journal of Current Research, 2014) Biira, Saphina; Kilama, George
Solar energy is an alternative to fossil fuels for more huge potential to meet many times the present world energy demand. Readily available solar radiation data is a key to design and simulation of all solar energy applications hour data is considered which were obtained from the meteorological Department, Entebbe. The sunshine hour’s data got were measurements from 2007 to 2012, from three stations of Jinja, Soroti and Kasese. These stations are well spread throughout the country a view of the level of solar radiation in the country. It was observed that Soroti had high monthly averages compared to Jinja and Kasese with three minima occurring in April, July and November. This analysis revealed that June to August in all the three stations. Low sunshine hours are encountered from November to December and lowest March to May. the distribution of mean sunshine interval from the three stations indicate that more sunshine occurred in Soroti with the average value of all the data recorded between 2007 and 2012 being 8.2 followed by Jinja with a value of 7.1 and finally Kasese with the lowest value of 6.1 hours. lower interval range is observed across all the months implying that overcast days were either followed by a clear or partially clear days. Therefore Uganda encounters bright sunshine days most of the time in the year
Concentration levels of radon in mines, industries and dwellings in selected areas of Tororo and Busia districts, Eastern Uganda
(Advances in Applied Science Research, 2014) Biira, Saphina; Kisolo, Akisophel W.; Mutonyi D’ujanga, Florence
Concentration levels and effective exposure dose of radon were determined in mines, industries and dwellings in the Districts of Tororo and Busia, Eastern Uganda in 60 indoor structures between November 2010 and April 2011, using activated charcoal canisters and sodium iodide detector. This study was undertaken to assess the radiological risk of radon exposure in selected areas in Eastern Uganda. The radon concentration levels were found to vary from 28±1 to 97±5 Bqm-3 and the effective dose varied from 0.71±0.03 to 2.44±0.13 mSvy-1, respectively. Over all the mean radon concentration values reported were all below the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and International Commission on Radiological Protection (ICRP) recommended radon action level of 200 Bqm-3. Some average radon concentration values were close 100 Bqm-3 an action level recommended by World Health Organization (WHO). This means radon levels are still within limits, however necessary mitigation measures need to be taken so that radon levels are not elevated beyond the mean values reported in this work.
Concentrations and human health risk assessment of selected heavy metals in soils and food crops around Osukuru phosphate mine, Tororo District, Uganda
(Toxicology Reports, 2022) Tagumira, Abudallah; Biira, Saphina; Amabayo, Emirant Bertillas
This study investigated the concentrations of heavy metals, particularly chromium (Cr), cadmium (Cd); lead (Pb), copper (Cu), and iron (Fe) in the soil and crops. The accumulation of heavy metals in the crop system, the probable daily intake of heavy metals, and the assessment of potential health threats associated with the uptake of metals by the residents around the Osukuru phosphate mine in Tororo, Uganda. The concentrations were assessed with the assistance of an Atomic Absorption Spectrometer (AAS). The crops studied were amaranthus (Amaranthus hybridus) leaves, pumpkin (Cucurbita pepo) leaves, maize (Zea mays) grains, and cowpeas (Vigna unguiculata) leaves. A total of 200 samples were collected from five villages of Osukuru Sub County. The findings of this study showed that elemental concentrations of heavy metals in the soil were within the standard recognized limit for agriculture as documented by World Health Organization (WHO) and European Union (EU). While more noticeable levels of these elements were detected in crop samples, especially amaranthus. Chromium composition was lower than the detection level in all samples. The transfer factor results showed elemental intake by the crops in the sequence; Fe > Cu > Cd > Pb. The probable daily intakes of the elements were below the daily threshold values endorsed by WHO/FAO. The health threat index showed high values for Pb and Cd from maize but low values of Cu and Fe in all samples and therefore these crops may not be very safe for human intake.
Effect of the ZrCl4 static vaporiser system and deposition time on growth characteristics of chemical vapour deposited zirconium carbide layers
(Applied Physics A, 2019) Biira, Saphina; Hlatshwayo, Thulani T.; Crouse, Philip L.; Bissett, Hertzog; Thabethe, Thabsile T.; Mlambo, Mbuso; Malherbe, Johan B.
ZrC layers were deposited from ZrCl4– Ar–CH4–H2 gas mixture in a home-built vertical wall chemical vapour deposition system within the deposition time range 0.5–2.5 h. The flow behaviour of ZrCl4 from the static vaporiser system to reaction chamber as a function of time was studied. To investigate the microstructure evolution and the growth characteristics of ZrC layers with deposition time, the growth rate, microstructure, morphology and composition were analysed. The layer thickness increased with deposition time all through; however, its growth rate increased up to 1.0 h and thereafter declined. The X-ray diffraction (XRD) analysis showed both ZrC and carbon peaks. The intensity of the carbon peaks followed a non-linear trend with deposition time. The average crystallite size and the number of crystallites per unit volume of the layers increased with deposition time. The orientation of crystallographic plane also varied with the deposition time. At short deposition times, the Raman spectra showed the acoustic and optic branches indicating that the ZrC deposited contained carbon vacancies. The D and G peaks of carbon increased as the deposition time increased, an indication of free carbon in the deposited layers. At short deposition times, the surface morphology of the layers was relatively flat and smooth. The particle size and agglomerations also increased with time.
Evaluation of radionuclide concentrations and average annual committed effective dose due to medicinal plants and soils commonly consumed by pregnant women in Osukuru, Tororo (Uganda)
(Journal of Environmental Radioactivity, 2021) Biira, Saphina; Ochom, Peter; Oryema, Bosco
The intention of the study was to establish the activity concentrations and the annual committed effective dose due to ingestion of medicinal plants and soils by pregnant women and their probable effects to infants. The samples of medicinal plants and soils were collected from Osukuru, Tororo District (Uganda). The naturally occurring radionuclides investigated were 226Ra, 232Th and 40K and their activity concentrations were determined using NaI gamma detector. In the medicinal plants, the average activity concentrations of 226Ra, 232Th and 40K were found to be 6.04 Bq/kg, 9.65 Bq/kg and 359.59 Bq/kg respectively. African Basil registered the highest activity concentration of 226Ra of 10.02 Bq/kg, spider plant had the highest activity concentration of 232Th of 18.60 Bq/kg whereas the pumpkin registered the highest activity concentrations of 40K of 437.92 Bq/kg. The average activity concentrations of 226Ra, 232Th and 40K in ‘medicinal soils’ were 68.87 Bq/kg, 78.20 Bq/kg and 477.44 Bq/kg respectively. The soils from the anthills registered the highest activity concentration of 226Ra and 40K while the one from bricks registered the highest activity concentration of 232Th. The annual committed effective dose due to the ingestion of medicinal plants varied from 0.096 to 0.297 mSv/ y with an average of 0.194 mSv/y in infants, 0.016–0.040 mSv/y with an average of 0.029 mSv/y for individuals of age range 12–17 years and 0.007–0.018 mSv/y with an average of 0.013 mSv/y for individuals older than 17 years. Whereas the annual committed effective dose due to the ingestion of ‘medicinal soils’ varied from 1.28 to 1.65 mSv/y with an average of 1.46 mSv/y in infants, 0.23–0.30 mSv/y with an average of 0.26 mSv/y (12–17 years) and 0.07–0.09 mSv/y with an average of 0.08 mSv/y for individuals older than 17 years. In medicinal plants, the annual committed effective dose for the all age groups examined were below 0.3 mSv/y (maximum world permissible as reported UNSCEAR, 2000) while that due to the ingestion of ‘medicinal soils’ had values higher 0.3 mSv/y in infants. The results of this study show that there is inherent danger to the infants in consuming soils during pregnancy and this should be discouraged.
Female Physicists in Ugandan Universities
(In AIP Conference Proceedings, 2015) D’ujanga, Florence M.; Ssentongo, Grace Spencer; Ayugi, Gertrude; Akoba, Rashida; Biira, Saphina
For a long time, only one public university in Uganda had a department of physics. Several women graduated from this department, but not many showed much interest in pursuing higher degrees in physics. Currently, there are five public universities in Uganda with departments of physics, and there has been an increase in the number of female graduates in physics. At the same time, the number of women pursuing higher degrees in physics has increased, and the universities have registered an increase in female physics lecturers.
Formation of Color Centers and Concentration of Defects in Boron Carbide Irradiated at Low Gamma Radiation Doses
(Journal of the Korean Physical Society, 2018) Mirzayev, Matlab Nabi; Mehdiyeva, Ravan Nadir; Zellabdin Melikova, Sevinj; Hamid Jabarov, Sakin; Theodora Thabethe, Thabsile; Biira, Saphina; Abdulla Kurbanov, Mirze; Van Tiep, Nguyen
In the present work, boron-carbide (B4C) samples (purity of 99.5% and density of 1.80 g/cm3) were irradiated by using gamma radiation from a 60Co gamma source. Gamma irradiation of the samples was carried out at doses 48.5, 97, 145.5 and 194 kGy. The samples were analysed using a UV-V Gary 50 Scan spectrophotometer. The effect of different irradiation doses on the defects created in the B4C samples was investigated. In the B4C samples, the formation processes for color centers depended on the gamma irradiation dose. The calculated activation energies at room temperature essential for the formation of F and F+ color centers ranged from 1.89 - 2.05 eV.
Investigating the thermal stability of the chemical vapour deposited zirconium carbide layers
(Journal of Alloys and Compounds, 2020) Biira, Saphina; Thabethe, T.T.; Hlatshwayo, T.T.; Bissett, H.; Ntsoane, T.; Malherbe, J.B.
The effect of thermal treatment on zirconium carbide (ZrC) layers deposited by chemical vapour deposition process was investigated using X-ray diffraction (XRD), Raman spectroscopy, nanoindention and scanning electron microscopy (SEM). The ZrC layers deposited at 1400 C (composed of 96% ZrC and 4% C) were annealed at 1500, 1600, 1700 and 1800 C for 2 h under high vacuum of 2.6 10 7 mbar. After annealing, the lattice constant and the average crystallite sizes were found to increase whereas the lattice strain and dislocation density decreased. The preferred orientation of the as-deposited layers was (220); it changed to (200) when annealed at 1500 C and 1600 C. At annealing temperature of 1700 C and 1800 C, the preferred orientation was (220) just like for the as-deposited ZrC layers. From Raman spectroscopy analysis, the ID/IG ratio reduced from 0.694 to 0.414 with annealing temperature indicating an improvement in crystallinity level and a decrease in the defects in the carbon material in the ZrC layers. The hardness of the layers was found to decrease slightly with annealing temperature from 26.4 ± 0.6 GPa to 21.3 ± 0.5 GPa. Some voids initially present in the as-deposited ZrC layers closed up and particles increased in size with annealing temperature.
A Mathematical Model Approach for Prevention and Intervention Measures of the COVID19 Pandemic in Uganda
(BMJ, 2020) Mbabazi, Fulgensia Kamugisha; Gavamukulya, Yahaya; Awichi, Richard; Olupot, Peter Olupot; Rwahwire, Samson; Biira, Saphina; Luboobi, Livingstone S.
The human–infecting corona virus disease (COVID–19) caused by the novel severe acute respiratory syndrome corona virus 2 (SARS–CoV–2) was declared a global pandemic on March 11th, 2020. Current human deaths due to the infection have raised the threat globally with only 1 African country free of Virus (Lesotho) as of May 6th, 2020. Different countries have adopted different interventions at different stages of the outbreak, with social distancing being the first option while lock down the preferred option for flattening the curve at the peak of the pandemic. Lock down is aimed at adherence to social distancing, preserve the health system and improve survival. We propose a Susceptible–Exposed–Infected–Expected recoveries (SEIR) mathematical model to study the impact of a variety of prevention and control strategies Uganda has applied since the eruption of the pandemic in the country. We analyze the model using available data to find the infection–free, endemic/infection steady states and the basic reproduction number. In addition, a sensitivity analysis done shows that the transmission rate and the rate at which persons acquire the virus, have a positive influence on the basic reproduction number. On other hand the rate of evacuation by rescue ambulance greatly reduces the reproduction number. The results have potential to inform the impact and effect of early strict interventions including lock down in resource limited settings and social distancing.
A Mathematical Model Approach for Prevention and Intervention Measures of the COVID{19 Pandemic in Uganda
(Asian Research Journal of Mathematics, 2022) Kamugisha Mbabazi, Fulgensia; Gavamukulya, Yahaya; Awichi, Richard; Olupot-Olupot, Peter; Rwahwire, Samson; Biira, Saphina; Luboobi, Livingstone S.
The human{infecting corona virus disease (COVID{19) caused by the novel severe acute respiratory syndrome corona virus 2 (SARS{CoV{2) was declared a global pandemic on March 11th, 2020. Current human deaths due to the infection have raised the threat globally with only 1 African country free of Virus (Lesotho) as of May 6th, 2020. Different countries have adopted different interventions at different stages of the outbreak, with social distancing being the first option while lock down the preferred option for flattening the curve at the peak of the pandemic. Lock down is aimed at adherence to social distancing, preserve the health system and improve survival. We propose a Susceptible{Exposed{Infected{Expected recoveries (SEIR) mathematical model to study the impact of a variety of prevention and control strategies Uganda has applied since the eruption of the pandemic in the country. We analyze the model using available data to find the infection{free, endemic/infection steady states and the basic reproduction number. In addition, a sensitivity analysis done shows that the transmission rate and the rate at which persons acquire the virus, have a positive influence on the basic reproduction number. On other hand the rate of evacuation by rescue ambulance greatly reduces the reproduction number. The results have potential to inform the impact and effect of early strict interventions including lock down in resource limited settings and social distancing.
Quantification and characterization of cocoa pod husks for electricity generation in Uganda
(Sustainability and Society, 2019) Kilama, George; Lating, Peter O.; Byaruhanga, Joseph; Biira, Saphina
Due to limited coverage, the electricity power supply in Uganda is an obstacle to the country’s economic development. Utility firms in Uganda either lack the financial capacity to expand their grids to isolated rural areas or choose not to do so due to the low return on investment. Therefore, connecting households to minigrids represents an effective solution to providing power to remote/rural areas. This study evaluates the resource and technology of generating electrical energy from cocoa pod husks (CPHs), an agricultural residue/waste, generated in Uganda. The use of agricultural waste for energy generation is the most suitable option for the rural population in Uganda because of the availability of a raw material (biomass) for its production, which is pollutionfree (renewable and clean) and does not have competition for use. The inability to convert these solid wastes into useful products culminates into environmental related challenges, such as landfilling, climate change, pests, and diseases. Therefore, the aim of this study is to quantify the amount of generated CPHs and evaluate its potential for electricity generation in Uganda. Subsequently, we have been looking into the potential of CPHs as a feedstock for a thermochemical conversion process and the feasibility of a direct combustion technology. Results: The amount of CPHs generated in Uganda has been estimated. The physiochemical analysis has shown that the proportion of CPHs in the fresh pods is about 74%, which is nearly the same as in other studies. The dry matter content of CPHs has been found to be on an average of 19%, whereas ash content, moisture content, and the gross caloric value have been recorded to be 12.3%, 12.58%, and 17.5%, respectively. It seems therefore likely that 41.7 GJ of energy might be produced each year from CPHs in Uganda. Conclusion: This study has demonstrated that the CPHs are an important energy source. As there is an increasing trend in cocoa and CPH production in Uganda per year, the electricity production based on CPHs is sustainable and can be upgraded. The use of CPHs for energy conversion is therefore feasible, cost-efficient, and a solution to some environmental challenges.
Thermal Performance Evaluation of the Funnel Solar Cooker of Different Funnel Lengths Implemented in Nagongera, Uganda
(Tanzania Journal of Science, 2020) Chepkurui, Jonah; Biira, Saphina
The aim of this study was to evaluate the thermal performance of a funnel solar cooker with different funnel lengths. Four funnel solar cookers of varying funnel lengths were constructed at Nagongera, in Tororo District, Uganda from cheap locally available materials. After construction, four blacked cooking pots of the same size filled with 1 kg of water were each placed in a cooker from 09:00 to 17:00 hrs. The temperature of the water in the pots was recorded after every 2 hours. The maximum temperatures of 93 °C, 84 °C, 68 °C and 58 °C for the funnel lengths of 50 cm, 42.6 cm, 32 cm and 23.3 cm, respectively were achieved at 13: 00 hrs for the average solar intensity of 684 W/m2 and ambient temperature of 27.9 °C. Similarly, as the funnel lengths increased from 23.3 cm to 50 cm, the thermal efficiency of the cooker increased from to 29.2% to 33.2% due to increased solar collecting surface. This indicates that the cooking temperature and thermal efficiency depended on the funnel lengths of the cooker and the time of the day. The results obtained were suitable and therefore the funnel solar cooker can be introduced to the community.
Thermodynamics kinetics of boron carbide under gamma irradiation dose
(International Journal of Modern Physics B, 2019) Mirzayev, Matlab; Demir, Ertugrul; Mammadov, Khagani; Mehdiyeva, Ravan; Jabarov, Sakin; Tugrul, A. Beril; Biira, Saphina; Tiep, Nguyen; Thabethe, Thabsile
In this paper, high purity boron carbide samples were irradiated by 60Co gamma radioisotope source (0.27 Gy/s dose rate) with 50, 100, 150 and 200 irradiation hours at room-temperature. The unirradiated and irradiated boron carbide samples were heated from 30 C to 1000 C at a heating rate of 5 C/min under the argon gas atmosphere of ow rate 20 ml/min. Thermogravimetric (TG) and Differential Scanning Calorimetry (DSC) were carried out in order to understand the thermodynamic kinetics of boron carbide samples. The weight kinetics, activation energy and specific heat capacity of the unirradiated and irradiated boron carbide samples were examined in two parts, T 650 C and T 650 C, according to the temperature. The dynamic of quantitative changes in both ranges is different depending on the irradiation time. While the phase transition of unirradiated boron carbide samples occurs at 902 C, this value shifts upto 940 C in irradiated samples depending on the irradiation time. The activation energy of the unirradiated boron carbide samples decreased from 214 to 46 J/mol in the result of 200 h gamma irradiation. The reduction of the activation energy after the irradiation compared to the initial state shows that the dielectric properties of the irradiated boron carbide samples have been improved. After the gamma irradiation, two energy barrier states depending on the absorption dose of samples were formed in the irradiated samples. The rest and second energy barriers occurred in 0.56{0.80 and 0.23{0.36 eV energy intervals, respectively. The existence of two energy levels in the irradiated boron carbide indicates that the point defects are at deep levels, close to the valence band.
Trends and status of women in physics in Uganda
(AIP Publishing LLC, 2019) D’ujanga, Florence M.; Biira, Saphina; Akoba, Rashida
Most women in Uganda with an advanced degree in physics find employment at a university, teaching and conducting research. Very few take jobs in by industry or at government research laboratories. This paper discusses the trends in Uganda in women’s participation in the field of physics and their status. The paper also highlights factors that hinder girls from pursuing the study of physics and describes interventions the government is initiating to alleviate the situation.

Browsing by Author "Biira, Saphina"

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