Tanzania Journal of Science https://www.ajol.info/index.php/tjs <p><strong><em>Tanzania Journal of Science</em></strong> (<em>Tanz. J. Sci.</em>)&nbsp; is an <strong>international journal</strong> published by the College of Natural and Applied Sciences, University of Dar es Salaam. The <strong><em>Tanzania Journal of Science</em></strong>,&nbsp;formerly known as “<em>University Science Journal", </em>was established in 1975 as a forum for communication and co-ordination between and among scientists and allied professionals. It is also intended as a medium for dissemination of scientific knowledge among scientists and the public at large to promote the advancement of pure and applied sciences. Tanzania Journal of Science publishes high quality contributions on original works in the fields of pure and applied sciences. Its review processes and decision criteria are rigorous. The manuscripts are evaluated by expert reviewers and editors to assess their scientific quality. Those manuscripts judged by the editors and Chief Editor to be of insufficient scientific quality or interest, or generally inappropriate are rejected promptly without formal review. Also, manuscripts not complying with the journal requirements and author guidelines are returned to the authors or rejected. The decisions regarding acceptance or rejection of papers are independent, unbiased and fair.&nbsp;</p> <p>Indexed/Abstracted in: African Journals OnLine (AJOL); CAB International or CABI (Centre for Agriculture and Bioscience International, UK); CAB Direct; CAB Abstracts; CAB Global Health; Google Scholar; Journals for Free (J4F) database</p> <p><strong>For online submission please <a href="https://tjs.udsm.ac.tz/index.php/tjs/onlinesubmission" target="_blank" rel="noopener">click here</a></strong></p> College of Natural and Applied Sciences (CoNAS) of the University of Dar es Salaam (UDSM) en-US Tanzania Journal of Science 0856-1761 <p>Copyright for articles published in this journal is retained by the journal.</p><p>This journal provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge</p> Copper slag as a potential waste filler for polyethylene-based composites manufacturing https://www.ajol.info/index.php/tjs/article/view/207026 <p>The present study aimed to analyze the application of waste material from copper production– copper slag (ŻŻL) as filler for composites based on the high-density polyethylene (HDPE). Copper slag filler was introduced in the amounts of 1–20 wt%, and its influence on the appearance (color analysis), chemical structure (Fourier-transform infrared (FTIR) spectroscopy), microstructure (optical microscopy), as well as static (tensile tests) and dynamic (dynamical mechanical analysis (DMA)) mechanical properties of composites were investigated. Proper dispersion of filler implicated that the incorporation of up to 5 wt% of filler caused only slight, 5% drop of tensile strength, with the simultaneous 16% rise of Young’s modulus. Further increase of filler loading resulted in higher values of porosity and the rise of the adhesion factor, determined from DMA results, which led to the deterioration of mechanical performance. Moreover, spectroscopic analysis of PE-ŻŻL composites indicated that the analyzed filler might be applied as a coloring agent, and the appearance of composites may be engineered by adjustment of filler loading.</p> <p><strong>Keywords</strong>: polyethylene, copper slag, mechanical properties, structure, composite, particle reinforced composite</p> Aleksander Hejna Paulina Kosmela Mateusz Barczewski Olga Mysiukiewicz Adam Piascki Copyright (c) 2021 2021-05-11 2021-05-11 47 2 405 420 10.4314/tjs.v47i2.1 Upgrading biogas using Eburru zeolitic rocks and other adsorbent materials to remove carbon dioxide and hydrogen sulphide https://www.ajol.info/index.php/tjs/article/view/207027 <p>The trace amounts of carbon dioxide and hydrogen sulfide in raw biogas lower its calorific value,<br>cause corrosion and make it hard to compress biogas into the cylinder. Raw biogas was obtained<br>from anaerobic digestion of cow dung and market wastes. The gas was stored in tubes or urine bag<br>before upgrading. Natural zeolite rocks, maize cobs, steel wire, desulphurizer, and worn-out tyres<br>were used as the upgrade materials. The composition of biogas was recorded before and after<br>upgrading using a GP180 portable biogas analyzer from Henan, China. The measured level of raw<br>biogas was 0.0227% H2S, &gt;20% CO<sub>2</sub> and 52-56% CH<sub>4</sub>. The most efficient upgrade materials were<br>zeolite rocks with upgrade levels of 89–93% methane. The total removal using zeolite was<br>observed to be 75% CO<sub>2</sub> and 95.34% H<sub>2</sub>S. The morphological structures of zeolitic rocks account<br>for its higher upgrading properties compared to other materials. In addition, the porosity in these<br>rocks mean that CO<sub>2</sub> and H<sub>2</sub>S were adsorbed resulting in high CH<sub>4</sub> levels in the upgraded biogas.<br>Other adsorbents showed upgrading properties with removal rates above 70% for both H<sub>2</sub>S and<br>CO<sub>2</sub>.</p> <p><strong>Keywords</strong>: Biogas, Upgrading, Natural zeolite, Bio-methane</p> James K Mbugua Joseph M Mwaniki Damaris M Nduta Francis B Mwaura Copyright (c) 2021 2021-05-11 2021-05-11 47 2 421 431 10.4314/tjs.v47i2.2 Thermodynamic analysis of a variable viscosity reactive hydromagnetic couette flow within parallel plates https://www.ajol.info/index.php/tjs/article/view/207028 <p>This investigation is to consider the impact of a temperature-dependent variable viscosity of a reactive hydromagnetic Couette fluid flowing within parallel plates. The variable property of the fluid viscosity is thought to be an exponential relation of temperature under the impact of magnetic strength. The differential equations controlling the smooth movement of fluid and energy transfer are modeled and solved by using the series solution of modified Adomian decomposition technique (mADM). The outcomes are shown in tables and graphs for different estimations of thermophysical properties present in the flow regime together with the rate of entropy generation and irreversibility distribution outcome.</p> <p><strong>Keywords</strong>: Reactive fluids, Couette Flow, variable viscosity, hydromagnetic and modified Adomian decomposition method (mADM).</p> Anthony R Hassan Olufemi W Lawal Funmilayo F Amurawaye Copyright (c) 2021 2021-05-11 2021-05-11 47 2 432 441 10.4314/tjs.v47i2.3 Mapping of geological structural features in Lolgorien, Narok County, Kenya: Using hillshade analysis https://www.ajol.info/index.php/tjs/article/view/207029 <p>Despite Lolgorien being one of the most active gold mining areas in Kenya, it is one of the most geologically understudied areas. To the best knowledge of the authors, Lolgorien geological map was last updated in the 1940s. Current technologies such as remote sensing allow new structural features such as faults to be easily identified. In this regard, this study employed remote sensed data to map structural features found in and around Lolgorien Subcounty, Narok, Kenya. This was done to identify any new structural features that might have been missed in the past. Shuttle Radar 152 Topography Mission Digital Elevation Model (SRTM-DEM) image was downloaded and analysed using hillshade technique. From this analysis, the research identified new structural features which were not included in the current geological map but exist on the ground. One such structural feature (fault) is located approximately at 9866237, 703601 (Universal Transverse Mercator, UTM coordinates) and trends in NW–SE direction. The study also found that most of the lineaments are concentrated in the southern part of Lolgorien area and around or at areas dominated by the banded iron formations. Petrographic analysis of the few samples collected from the area showed presence of gold, pyrite and chalcopyrite mineralisation.</p> <p><strong>Keywords</strong>: SRTM-DEM, lineaments, geological structures, hillshade analysis, Lolgorien area</p> <p>&nbsp;</p> Sammy O Ombiro Akinade S Olatunji Eliud M Mathu Taiwo R Ajayi Copyright (c) 2021 47 2 442 456 10.4314/tjs.v47i2.4 Analysis and comparison of optical performance and collectible solar energy between multi-sectioned compound parabolic concentrator (CPC) and restricted exit angle CPC https://www.ajol.info/index.php/tjs/article/view/207030 <p>This study was conducted to analyse and compare the optical performance and collectible solar radiation energy of two different Compound Parabolic Concentrators (CPCs): multi-sectioned CPC (hereafter called M-CPC) and restricted exit angle CPC (hereafter called R-CPC) so as to ascertain the best CPC for photovoltaics applications. For easy comparison between M-CPC and R-CPC, a standard CPC (hereafter called S-CPC) was also designed. A detailed ray trace simulation analysis was undertaken to compare ray trace diagrams, angular acceptance, optical efficiency and energy flux distribution of the three CPCs. Results indicated that the angular acceptance and optical efficiency of the three CPCs were the same (100%) between 0º and 15º incidence angles, but significantly varied above 15º. On the other hand, solar radiation distribution on the solar cell was more uniform for the M-CPC than that of S-CPC and R-CPC. In terms of annual solar radiation collection, results indicated that both S-CPC and M-CPC collected approximately the same amount of energy (49,500 W/m2). Furthermore, the energy collected by S-CPC or M-CPC was higher than that collected by R-CPC by about 23%. Therefore, based on the energy flux distribution and collectible solar radiation energy, M-CPC is the best concentrator for photovoltaics applications.</p> <p><strong>Keywords</strong>: Multi-sectioned CPC, restricted exit angle CPC, optical performance, collectible solar radiation energy</p> Damasen Ikwaba Paul Copyright (c) 2021 47 2 457 471 10.4314/tjs.v47i2.5 Assessment of fluoride bioaccumulation potential in African Catfish (Clarias gariepinus) reared in fluoride rich water https://www.ajol.info/index.php/tjs/article/view/207031 <p>Fluoride bioaccumulation in fish poses a significant impact on their growth, survival and consequently to upper trophic levels. Few studies have reported the impacts of high fluoride concentrations and their accumulation potential to catfish in African settings. A 60-day catfish cultivation was conducted at Ngarenanyuki ward and the Nelson Mandela African Institution of Science and Technology (NM-AIST) in Arusha, Tanzania to determine fluoride bioaccumulation and its impacts to catfish growth and survival. Juvenile catfish were exposed to 36 mg F–/L pond water and synthetic water containing fluoride (NaF) concentrations of 5, 15, 36 and 45 mg/L in aquaria set at NM-AIST laboratory. Fluoride concentrations in fish tissues were analysed by ion-selective electrode. Fish survival rate was greater than 90% in ≤ 36 mg/L fluoride levels compared to 65.8% in 45 mg F–/L aquarium. Significant fluoride bioaccumulation was observed in fish bones (222.00 mg/kg, dry weight), gills (177.4 mg/kg), skin (9 mg/kg) and low amount in fillets (1.467 mg/kg). Fluoride bioaccumulation significantly rose with fluoride levels increase and exposure time (p = 0.000). The study concludes that high fluoride occurrence and its increased exposure time increases fluoride bioaccumulation in African catfish. Therefore, growing catfish in water containing ≥ 45 mg F–/L requires defluoridation process.</p> <p><strong>Keywords</strong>: African catfish, Aquarium, Fluoride bioaccumulation, Growth performance</p> Jophillene Bejumula Revocatus L Machunda Liliane J Pasape Kelvin M Mtei Copyright (c) 2021 47 2 472 484 10.4314/tjs.v47i2.6 Amending traditional substrate rice straw with agroforestry tree foliage increases production cycle and nutritional value of Pleurotus floridanus https://www.ajol.info/index.php/tjs/article/view/207032 <p>The recent heightened attention on mushrooms has not considered shortening the production time and increasing nutritional value using substrates from agroforestry trees in addition to traditionally used agro-industrial residues. This study therefore, examined harvesting time, protein and essential minerals of <em>Pleurotus floridanus</em> grown on rice straw amended with<em> Gliricidia sepium</em> foliage in Morogoro, Tanzania. Mushrooms were cultivated in 30 x 40 cm 4 kg dry weight polythene bags in randomized complete block design (RCBD) experiment. Results showed that the addition of 5% <em>G. sepium</em> into rice straw reduced total time between spawning and first harvest of <em>P. floridanus</em>. <em>Gliricidia sepium</em> increased significantly (P &lt; 0.05) protein contents of the mushrooms by up to 40%. The addition of 5–10% <em>G. sepium</em> into rice straw increased significantly (P &lt; 0.05) manganese, copper and zinc in the mushrooms. The decrease in production time and high increase in protein and mineral contents indicate that agroforestry trees have the potential to increase production cycles and nutritional value of <em>P. floridanus</em>. Therefore, use of foliage from agroforestry trees in combination with traditional substrates for mushroom production could help fight malnutrition, improve food security and enhance income.</p> <p><strong>Keywords</strong>: Food security; <em>Gliricidia sepium</em>; Income; Mushrooms; Smallholder farmers</p> Samora M Andrew John R Mbwambo Copyright (c) 2021 47 2 485 494 10.4314/tjs.v47i2.7 Count time series models for road traffic accidents in Tanzania Mainland https://www.ajol.info/index.php/tjs/article/view/207033 <p>A pairwise analysis was conducted to assess the trends and factors associated with road traffic accidents in Tanzania. The Poisson and Negative Binomial Autoregressive Models were used to extend log linear functions by accounting time-varying components. A total of 85,514 road traffic accidents in Tanzania mainland that occurred from 2012 to 2017 were extracted from Tanzania Police Office records. Eleven factors were grouped into a human, vehicle, physical/environmental and pedestrian-related factors. The Likelihood ratio test, Akaike Information Criterion, Bayesian Information Criterion and residual ACF plots were used to evaluate the performance of the models in Dar es Salaam and other combined regions. The trend analysis indicated a declining pattern in all factors and human-related factors appeared higher than the other three factors. The highest number of road traffic accidents was observed in Dar es Salaam Region compared to other combined regions. The models, including its past values and time-varying factors, were in favour-of other models. In both, Dar es Salaam and other combined regions, non-linear pattern and Negative Binomial Autoregressive Models fitted the data well. The implementation of collective actions in recent years seems positive on road traffic accidents. Nevertheless, more emphasis is needed to monitor trends on the number of accidents and related fatalities.</p> <p><strong>Keywords</strong>: Road Traffic Accidents, Poisson, Negative binomial, Autoregressive Models, Tanzania.</p> Amina S Msengwa Florence D Ngari Copyright (c) 2021 47 2 495 506 10.4314/tjs.v47i2.8 A GATE-based Monte Carlo simulation of a dual-layer pixelized gadolinium oxyorthosilicate (GSO) detector performance and response for micro PET scanner https://www.ajol.info/index.php/tjs/article/view/207034 <p>The purpose of this study was to simulate the GSO detector of a micro PET using GATE simulation platform. The performance and responses of the simulated GSO detector assembly were evaluated by comparing the simulated data to the experimental and XCOM data to validate the simulation platform and procedure. Based on NEMA NU-4 2008 protocols, the performance of GSO detector in terms of sensitivity was simulated and compared to the experimental data. Similarly, the GSO detector response to photons interaction was simulated and compared against the XCOM data for absorbed intensity ratio in the GSO detector and survived intensity ratio in Pb blocks. Results showed that simulated and experimental sensitivities agreed well with R2 of 0.995 and two overlapping bands at 95% confidence. An agreement with R2 of 0.972 and 0.973 as well as with overlapping bands at 95% confidence was obtained in simulated and XCOM data for absorbed and survived intensity ratio in the GSO detector and Pb blocks, respectively. The observed agreements demonstrate the accuracy of the simulation method to mimic the behaviour of the GSO detector. The validated GATE algorithm for micro PET scanner is therefore recommended for simulation and optimisation of collimator design in further studies.</p> <p><strong>Keywords</strong>: GATE simulation, Experimental data, XCOM data, GSO detector, micro PET.</p> <p>&nbsp;</p> Leonid L Nkuba Innocent J Lugendo Idrissa S Amour Copyright (c) 2021 47 2 507 519 10.4314/tjs.v47i2.9 Hydrogeophysical investigation for the aquifers in part of Ilorin, Central Nigeria: Implication on groundwater prospect https://www.ajol.info/index.php/tjs/article/view/207035 <p>Hydrogeophysical study involving the use of Vertical Electrical Sounding (VES) was carried out in part of the basement complex rocks of Ilorin, central Nigeria, with the aim of determining its geoelectric parameters and groundwater potential. A total of thirty (30) VES were carried out using Schlumberger electrode configuration, with half electrode separation (AB/2) varying from 1m to 100m. Information on the subsurface lithologies, overburden thickness and aquiferous layers were obtained from the different VES locations in the study area. From the quantitative interpretations of the data collected, using the method of curve matching with the Orellana-Mooney master curves and 1-D forward modeling with WinResist 1.0 version software, three to five lithologic units were identified in the study. These include: the topsoil, sandy/lateritic clay/laterite, the weathered basement, the fractured basement and the fresh bedrock which are predominantly of the ‘KH’ curve type (30%), followed by ‘H’ type (26.7%), other type curves include ‘QH’ (16.7%), ‘HKH’, ‘HA’ and ‘A’ (6.7% each) and KQ and KQH (3.3% each). The weathered layer and the fractured basement constitute the main aquifer units. The aquifers are of generally low resistivity values (mostly below 100 Ω-m). The depths to dry bedrock at the chosen VES locations vary from 2.7 to 62.7 m with a mean value of 13.02 m in the study area. The geoelectrical interpretations of data obtained in these areas have permitted the delineation of the study area into low and moderate groundwater potential zones. This study is expected to assist in future planning for groundwater resources.</p> <p><strong>Keywords</strong>: Hydrogeophysical, Basement Complex, Groundwater, Electrical Soundings, Weathered, Fractured</p> Ayodele Kehinde Olawuyi Copyright (c) 2021 2021-05-11 2021-05-11 47 2 520 534 10.4314/tjs.v47i2.10 Mineralogical and geochemical characteristics of graphite-bearing rocks at Chenjere Area, south-eastern Tanzania: Implications for the nature and quality of graphite mineralization https://www.ajol.info/index.php/tjs/article/view/207036 <p>This study focused on the mineralogical and geochemical characteristics of graphite-bearing rocks at Chenjere area by conducting surface geological mapping, geochemical and petrographical analyses with the intention of characterizing the nature of graphite occurrence in these lithological units. This paper presents results of the flake size, grade and mineralization extension of graphite in the graphitic gneiss. Field observations, petrographic investigation and comparison with other studies indicate that graphite occurrence at the Chenjere area is of sedimentary origin which fall under syngenetic type. The petrographic study revealed that nature of metamorphism of rocks in the Chenjere area is of high grade (amphibolite facies). Both field observations and petrographic studies indicate that minerals in the rock associated with graphite include quartz, feldspar (mostly K-feldspar) and biotite. Further, the mineralized zones are concordant to the rest of the lithologies of the area and biotite gneiss is forming the hangingwall and footwall. The rocks’ foliation is generally NE striking and dipping SE with the dip amount ranging from 30 to 60 degrees. The graphite mineralization at the study area occurs as medium to coarse grained crystalline, flake type graphite with long axis of up to 1000 micrometres in size. Graphite flakes are disseminated and oriented in the host rock that represents a normal metamorphic fabric. Geochemical results indicate that graphite contents in the host graphitic gneiss range from 3.03 wt.% to 16.00 wt.%. Mineralogy and texture of the graphite at Chenjere area meet the standards required for industrial applications in various advanced technologies.</p> <p><strong>Keywords</strong>: Graphite Mineralization, Flake Graphite, Chenjere Area</p> Charles D Moye Michael M Msabi Copyright (c) 2021 2021-05-11 2021-05-11 47 2 535 551 10.4314/tjs.v47i2.11 Geological controls on brine discharge in Itumbula Salt Dam within the Rukwa Rift in Momba District, Tanzania https://www.ajol.info/index.php/tjs/article/view/207037 <p>The Itumbula salt dam of the Rukwa Rift Basin is a depression formed through extraction of spring-derived salt crystals. Brine yield by springs which is the primary cause of significant amounts of salt in the dam required further geological investigations to understand yield controls. In this study, detailed field geological investigations in the salt dam and its surroundings were conducted to ascertain brine discharge controls. These included documentation of lithology and surface manifestations of brine deposition. Geophysical methods (i.e. magnetic and electric surveys) for studying geologic structures associated with brine deposits, and laboratory analysis of cations and anions (e.g. chlorides, bicarbonates or sulphates) essential to characterize composition of waters were also performed. The information on the springs discharge rate was retrieved from the previous studies. The magnetic profile revealed a very low magnetic anomaly across the salt dam, trending NW to SE direction, which is interpreted to be the main structure that controls fluid movements in the dam. Electric resistivity survey results delineated a low resistivity body in the central part of the dam interpreted as porous formation with saline water. Hydro-chemistry of the hot spring brines indicated high levels of sodium and chloride ions contents than magnesium, calcium, potassium, sulphate, and carbonate and bicarbonate ions, interpreted to be mature water with minimal water mixing. The structurally controlled brines of approximately 2.5 kg/s are discharged in the study area.</p> <p><strong>Keywords</strong>: Geologic Structures, Brine, Salt Production, Momba, Rukwa Basin.</p> Mwita S Maswi Octavian Minja Chakutema Batwenge Copyright (c) 2021 2021-05-11 2021-05-11 47 2 552 567 10.4314/tjs.v47i2.12 Coupled effects of hydrophilic nano silica oxide and anatase nano titanium oxide on strengths of oilwell cement https://www.ajol.info/index.php/tjs/article/view/207038 <p>The life of oil wells depends on the stability of cement sheath and bond strength with the formation and casing. Extreme subsurface conditions cause substantial stresses on the cement sheath resulting in a serious impact on well integrity. The recommended API cement for oilwell fails to provide the required durability of the cemented well due to such conditions. Supplementary cementitious materials such as nanoparticles are added to improve the cement for long-lasting zonal isolation. In this study, the compressive and shear bond strengths of oilwell cement containing nano-SiO<sub>2</sub> and nano-TiO<sub>2</sub> were studied at 80 °C for 3, 7, 14, and 28 days of hydration. The XRD, TG, and DSC were used for the analysis of cement hydration products. The results revealed that both nano-SiO<sub>2</sub> and nano-TiO<sub>2</sub> increased strength evolution. A ternary system made with 2% nano-SiO<sub>2</sub> and 2% nano-TiO<sub>2</sub> improved compressive strength by 22.6 and 48.4%, while the shear bond strength increased by 110.6 and 55% at age of 3 days and 28 days, respectively, compared to their corresponding binary systems. Therefore, these results remark the potential of replacing an appropriate proportion of oilwell cement with coupled nano-SiO<sub>2</sub> and nano-TiO<sub>2</sub> to ensure cement sheath structure durability in the annular and long-lasting zonal isolation.</p> <p><strong>Keywords</strong>: Nano-silica, nano-titanium, compressive strength, shear bond strength, oilwell cement</p> Petro E Mabeyo Jun Gu Copyright (c) 2021 2021-05-11 2021-05-11 47 2 568 582 10.4314/tjs.v47i2.13 Effects of Xanthan gum on rheological properties of Aloe vera-Moringa leaf juice blends https://www.ajol.info/index.php/tjs/article/view/207039 <p>Understanding the impacts of hydrocolloid agents on the rheological properties of nutraceutical beverages like Aloe vera-moringa juice blend is very useful for functional properties and product stability. To this end, the effects of xanthan gum on rheological properties in Aloe vera-moringa leaf juice blends were investigated using a Brookfield rheometer. Aloe vera-moringa leaf juice blends were prepared and then incorporated with xanthan gum at different ratios (w/w) of 0.2%, 0.4%, 0.6%, 0.8%, and 1%. The results revealed that the viscosity of Aloe vera-moringa juice blend was strongly affected by the xanthan gum addition. The viscosity profiles depicted a decreasing trend in viscosity when a shear rate increased. The Aloe vera-moringa leaf juice blend changes from a Newtonian fluid to the non-Newtonian fluid as the xanthan gum fraction increases. Moreover, shear stress was observed to increase with increasing in xanthan gum concentrations. For quantitative analysis, both Power-law and Bingham model equations were fitted to experimental data to easily describe the flow behaviour of the Aloe vera-moringa leaf juice blends. The juices added with xanthan gum of 0.4% to 1% were found to show a shear-thinning behaviour, since the flow behaviour index, n &lt; 1. This implies that the apparent viscosity decreases as the shear rate increases.</p> <p><strong>Keywords</strong>: Aloe vera juice, Moringa leaf juice, Xanthan gum, Rheological property, Nutraceutical beverage</p> Victor V Matabura Leonard MP Rweyemamu Copyright (c) 2021 2021-05-11 2021-05-11 47 2 583 596 10.4314/tjs.v47i2.14 Evaluation of petroleum hydrocarbons contamination in soils and groundwater using electrical resistivity and hydrochemical methods-Case study: Ayetoro, Osogbo southwestern Nigeria https://www.ajol.info/index.php/tjs/article/view/207040 <p>The presence of Petroleum Hydrocarbons (PHCs) in hand-dug wells has become a concern to the residents of Ayetoro area, Osogbo. Consequently, the detection of PHCs was evaluated using, nine Vertical Electrical Soundings (VES) and 2D electrical resistivity tomography surveys. Soil samples collected were analyzed for porosity and permeability. Hand-dug well water samples were screened for PHCs. VES revealed that second layer had high apparent resistivity of 14415.0 Ωm, indicating presence of PHCs that had penetrated to maximum depth of 19.1 m. The highest resistivity of the control points was 48.0 Ωm, indicating absence of PHCs. The 2D resistivity revealed highest value of 3622 Ωm and had migrated to a depth of 10.0 m. The porosity (0.40) and permeability (6.87516 x 10<sup>–4</sup> cm/s) were typical of silty clay which allowed passage of PHCs. Hydro-chemical analysis indicated presence of PHCs (0.50–11.00 mg/L). The study has established presence of PHCs in soils and hand-dug wells.</p> <p><strong>Keywords</strong>: Petroleum Hydrocarbons, Soil, Groundwater, Electrical resistivity tomography</p> Mutiu A Fakunle Muhydeen A Ibraheem Wasiu B Agbaje Luqman A Abidoye Copyright (c) 2021 2021-05-11 2021-05-11 47 2 597 608 10.4314/tjs.v47i2.15 Screening of aflatoxin-producing fungi in maize and groundnuts from three regions in Tanzania https://www.ajol.info/index.php/tjs/article/view/207354 <p>This study screened aflatoxin-producing fungi in maize and groundnuts from Dodoma, Singida and Iringa regions in Tanzania, and assessed the level of peoples’ awareness on aflatoxins health effects. One hundred and twenty samples (20 each crop) were collected and inoculated on Sabouraud dextrose agar and one hundred and eleven samples were observed to have fungal growths that were identified to belong to four genera, namely <em>Aspergillus, Rhizopus, Mucor </em>and <em>Dermatophyte</em> with occurrence frequencies of 75, 2.5, 5 and 10%, respectively. Among the four screened genera of fungi, Aspergillus was observed to be the major aflatoxin-producing fungi. Five species of genus <em>Aspergillus</em>, namely <em>A. flavus, A. parasiticus, A. niger, A. fumigatus, </em>and <em>A. terreus</em> were isolated with frequencies of 39.1, 10, 7.5, 15.8 and 2.5%, respectively. Macromorphology and micromorphology of isolated <em>Aspergillus</em> spp were also observed using a light microscope. Furthermore, it was noted that the prevalence of fungi and aflatoxins contamination is more in groundnuts than in maize. In terms of awareness in individuals concerning aflatoxins, only 34% respondents in Dodoma, 29.9% in Singida and 24% in Iringa were aware of aflatoxins. Therefore, the creation of awareness and sensitization on aflatoxins health effects to the people is an important part of intervention ways to forestall and control aflatoxins in Tanzania.</p> <p><strong>Keywords</strong>: Aflatoxins, Maize, Groundnuts, Aspergillus spp, A. flavus, A. parasiticus, A. niger, A. fumigatus and A. terreus</p> Kusiluka Agape Valence MK Ndesendo Sartaz Begum Copyright (c) 2021 2021-05-19 2021-05-19 47 2 609 615 10.4314/tjs.v47i2.16 Spatial distribution patterns of the populations of two subterranean termites (Blattodea: Termitidae) in eucalyptus (Myrtales: Myrtaceae) plantations https://www.ajol.info/index.php/tjs/article/view/207359 <p>The study was conducted in Afaka, Northern Guinea Savanna of Nigeria to determine the spatial distribution patterns of the populations of <em>Ancistrotermes</em> sp. and <em>Microtermes</em> sp. in <em>Eucalyptus camaldulensis</em> Dehnh, <em>Eucalyptus citriodora</em> Hook, <em>Eucalyptus cloeziana</em> F. and <em>Eucalyptus</em> <em>tereticornis</em> Muell plantations. Spatial distributions patterns of the two termite species populations were determined using indices such as ratios of population variance to mean, Lloyd’s index, Green coefficient, Taylor power and Iwao’s regression models. The values of variance to mean ratios, Lloyd’s index and Green coefficient showed that the populations of both termite species had aggregated distribution pattern in all the Eucalyptus species plantations. The distribution patterns of <em>Ancistrotermes</em> and <em>Microtermes</em> differed using Taylor’s and Iwao regression models. The values of R2 in Taylor’s model ranged from 0.02 to 0.99 for Ancistrotermes sp. and 0.29 to 0.99 for <em>Microtermes</em> sp., while in Iwao’s model, R<sup>2</sup> ranged from 0.10 to 0.96 for <em>Ancistrotermes</em> sp. and 0.08 to 0.98 for <em>Microtermes</em> sp. The information provided is vital to develop a sound pest management protocol for these termite species.</p> <p><strong>Keywords</strong>: Spatial distribution, Ancistrotermes sp., Microtermes sp., Aggregated, Taylor’s model, Iwao’s model</p> Olaniyi T Alamu Francis K Ewete Ayangbade E Ayandokun John A Ete Copyright (c) 2021 2021-05-19 2021-05-19 47 2 616 624 10.4314/tjs.v47i2.17 Pathological scanning of ochratoxigenic moulds impaired feed in vivo, towards conceptualizing their reverberations on different organs https://www.ajol.info/index.php/tjs/article/view/207362 <p>The role of ochratoxigenic moulds in causing several invasive diseases has been documented but little is known about the effects of these ochratoxigenic moulds contaminated feeds in a laboratory control experiment. This study therefore, examined the pathological effects of ochratoxigenic moulds contaminated feed in order to understand their reverberations on different organs. Thirty two albino rats were randomly assigned to four experimental treatments (T) with eight rats per treatment (T1, T2, T3 and T4). T1 and T2 were female and male control rats, respectively that were fed normal feed, while T3 and T4 were male and female experimental rats that were fed with ochratoxigenic moulds contaminated feed for a period of two weeks. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphate (ALP), acid phosphate (ACP), total protein, albumin and histopathological analysis of different organs, namely liver, heart, kidney, stomach, small intestine, lungs, brains and spleens were carried out following standard protocols. Results obtained depicted varying levels of serum concentrations of total protein, albumins, AST, ACP, ALT and ALP between treatments and control groups (p &lt; 0.05). Photomicrograph examinations of the different organs examined reveal degenerative changes in the ultra-structural integrity of all the organs as compared to the control groups except for the spleen where there was no difference between the control and the treatment group.</p> <p><strong>Keywords</strong>: Pathology, scanning, ochratoxigenic moulds, reverberations.</p> Benjamin T Thomas Omolara D Popoola Moses O Efuntoye Mercy O Coker Ahmed O Tajudeen Copyright (c) 2021 2021-05-19 2021-05-19 47 2 625 636 10.4314/tjs.v47i2.18 Effects of rapid thermal annealing on the properties of room-temperature oxygenated DC sputtered zinc thin films for CZTS solar cells application https://www.ajol.info/index.php/tjs/article/view/207364 <p>This work investigated the potential to achieve zinc oxide (ZnO) films for Cu2ZnSnS4 (CZTS) solar cells window layer at controlled annealing conditions as a potential approach to address elemental inter-diffusion in CZTS solar cells. This involved rapid thermal annealing (RTA) of room-temperature oxygenated DC sputtered zinc thin films in an ambient of nitrogen gas at different temperatures. Structural, morphological, optical, and electrical properties of these films were determined by X-ray diffractometer, Scanning Electron Microscopy, Ultraviolet-visible-near infrared spectrophotometer, and Hall Effect measurement, respectively. ZnO phases were observed after annealing the films over 150 °C. The films’ grains sizes improved with increasing RTA temperature. An exponential decrease in these films’ resistivity was observed with increasing RTA temperature attaining the lowest value at 300 °C. The bandgap and average solar transmittance of the films increased with increasing RTA temperature achieving values that are potential for applications in CZTS solar cells window layer at RTA temperatures beyond 200 °C.</p> <p><strong>Keywords</strong>: Sputtering; Rapid thermal annealing; Zinc oxide; Structural; Opt-electrical</p> Emmanuel R Ollotu Nuru R Mlyuka Margaret E Samiji Copyright (c) 2021 2021-05-19 2021-05-19 47 2 637 647 10.4314/tjs.v47i2.19 Bacterial growth inhibitory effects of Calotropis procera’s latex, leaves and roots extracts https://www.ajol.info/index.php/tjs/article/view/207365 <p>This study was conducted to evaluate in vitro antibacterial potential of water and ethanolic extracts from <em>Calotropis procera</em> roots, leaves and latex. The growth inhibitory effects of the extracts were tested against<em> Escherichia coli</em> using disc diffusion method. Amoxicillin was used as positive control, whereas ethanol and distilled water were used as negative controls. Results showed that water extracts from root, latex and leaves had 3.27 ± 0.14, 3.1 ± 0.21 and 2.38 ± 0.24 cm of maximum inhibition zones, while the ethanolic extracts showed 2.91 ± 0.19, 3.02 ± 0.16 and 0.84 ± 0.31 cm, respectively of maximum inhibition zones. The positive control; amoxicillin had 3.56 ± 0.09 cm of maximum inhibition zone. Post hoc tests revealed that roots, latex and conventional amoxicillin were equally effective in inhibiting <em>E. coli</em> growth. It further revealed that water extracts exhibited more growth inhibitory effects than ethanol extracts. No significant variations were observed on the <em>E. coli</em> growth inhibition due to the locations from where <em>C. procera</em> were collected. Generally, results indicated that <em>C. procera</em> inhibited the growth of <em>E. coli</em>. Thus its uses for the development of traditional and complementary medicines and further investigation on its biological activity on other microbes are highly recommended.</p> <p><strong>Keywords</strong>: Antibacterial, <em>Calotropis procera</em>, Diameter of inhibition zone. Escherichia coli, Plant crude extract, Traditional medicine.</p> Marco Baluhya Charles O Joseph Copyright (c) 2021 2021-05-19 2021-05-19 47 2 648 654 10.4314/tjs.v47i2.20 Larvicidal potency of Dioscorea sansibarensis leaf extract against vector mosquitoes: Anopheles gambiae s.s. and Culex quinquefasciatus https://www.ajol.info/index.php/tjs/article/view/207366 <p>Mosquitoes are responsible for transmission of illnesses of public health importance including malaria, lymphatic filariasis, dengue, chikungunya, and many other diseases caused by viruses. Vector control using synthetic insecticides has been the cornerstone for management of vector-borne diseases. However, the chemical based interventions have not been sustainable due to emergency of resistance against insecticides among disease vectors. Plant based mosquitocidal products can be potential alternative tools in vector control. Therefore, the present study aimed at exploring the larvicidal properties of Dioscorea sansibarensis leaf extract against malaria and lymphatic filariasis vectors; Anopheles gambiae s.s. and Culex quinquefasciatus. The larvicidal activities of Dioscorea sansibarensis were assessed following WHO test procedures. Ethanol leaf extract of Dioscorea sansibarensis was evaluated against all the four instar larvae stages of An. gambiae s.s and Cx. quinquefasciatus susceptible laboratory colonies. The highest larvicidal potency was shown against the 4th instar stages of both species with the LC50 values of 60.915 ppm and 80.700 ppm for Cx. quinquefasciatus and An. gambiae s.s., respectively. The respective LC95 values for Cx. quinquefasciatus and An. gambiae s.s. were 168.898 ppm and 249.295 ppm. This implies that the extract can be applied as mosquito larvicide should its impact on non-targeted species be established.</p> <p><strong>Keywords</strong>:<em> Dioscorea sansibarensis</em>; vectors, mosquitoes, Zanzibar yams, Dar es Salaam, Tanzania</p> Anitha Philbert Copyright (c) 2021 2021-05-19 2021-05-19 47 2 655 663 10.4314/tjs.v47i2.21 Assessment of natural radioactivity and radiation hazards of building materials in Kinondoni District, Dar es Salaam, Tanzania https://www.ajol.info/index.php/tjs/article/view/207421 <p>Natural radionuclides from building materials are one of the potential sources of external as well as internal radiation exposure to the human body. Currently, this exposure has been increasing since people spend more than 80% of their time indoors (ICRP 1991). Commonly used building materials from Kinondoni District were investigated using γ-spectrometry; their activity concentrations of <sup>226</sup>Ra, <sup>232</sup>Th and <sup>40</sup>K in Bq/kg were measured. The results showed that average values of activity concentrations of 226Ra, 232Th and 40K were 15.62, 21.51 and 237.99 Bq/kg, respectively. All the activity concentrations in the studied samples were lower than the world average values of 35 Bq/kg for <sup>226</sup>Ra, 30 Bq/kg for <sup>232</sup>Th and 400 Bq/kg for <sup>40</sup>K. The radium equivalent activity ( 𝑅𝑎<sub>𝑒𝑞</sub>), external ( 𝐻<sub>𝑒𝑥</sub>), internal hazard index ( 𝐻<sub>𝑖𝑛</sub>) and gamma activity concentration index (𝐼𝛾) were calculated to assess the radiological hazards due to presence of natural radionuclides in the building materials. The results showed that the average values of Raeq, Hex, and Iγ were 64.7 Bq/kg, 0.17, 0.21 and 0.24, respectively. These values were lower than the world criteria values 370 for Ra<sub>eq</sub>, ≤ 1 for Hex, ≤ 1 for H<sub>in</sub> and ≤ 1 for I<sub>γ</sub>, respectively. The obtained results indicated that all the investigated building materials were safe for inhabitants.</p> <p><strong>Keywords</strong>: Building materials, Natural radionuclides, Radiation hazards, Gamma ray spectrometry, Activity concentration</p> Huruma P Mammba Vitus A Balobegwa Alex P Muhulo Peter A Pantaleo Remigius A Kawala Copyright (c) 2021 2021-05-19 2021-05-19 47 2 664 673 10.4314/tjs.v47i2.22 Solving the University course timetabling problem using bat inspired algorithm https://www.ajol.info/index.php/tjs/article/view/207367 <p>Many mathematical optimization problems from real-life applications are NP-hard, and hence no algorithm that solves them to optimality within a reasonable time is known. For this reason, metaheuristic methods are mostly preferred when their size is big. Many meta-heuristic methods have been proposed to solve various combinatorial optimization problems. One of the newly introduced metaheuristic methods is a bat-inspired algorithm, which is based on the echolocation behaviour of microbats. Bat algorithm (BA) and its variants have been used successfully to solve several optimization problems. However, from the No-free Lunch Theorem, it is known that there is no universal metaheuristic method that can solve efficiently all optimization problems. Thus, this study work focused on investigating the usefulness of BA in solving an optimization problem called Course Teaching Problem (CTP). Since BA was originally designed to solve continuous problems, and CTP is a combinatorial optimization problem, a discrete version of BA for CPT has been proposed and tested using real-life data from the Dar es Salaam University College of Education (DUCE). The algorithm has produced promising results, as in each execution test, it generated a timetable in which all hard constraints were met and soft constraints were significantly satisfied within a few iterations.</p> <p><strong>Keywords</strong>: Combinatorial optimization, Timetabling problem, Metaheuristic algorithms, Bat algorithm.</p> Ushindi Limota Egbert Mujuni Allen Mushi Copyright (c) 2021 2021-05-19 2021-05-19 47 2 674 685 10.4314/tjs.v47i2.23 Synergistic effects of halide ions and Acacia senegal gum on the corrosion inhibition of mild steel in sulfuric acid solution https://www.ajol.info/index.php/tjs/article/view/207370 <p>The synergistic effects of halide ions, Br– and I– and Acacia senegal gum exudates on the corrosion inhibition of mild steel in 0.5 M sulfuric acid solution has been investigated by potentiodynamic polarization measurements and electrochemical impedance spectroscopy techniques. Results showed that Acacia senegal gum exudate moderately reduces the corrosion rate of mild steel. The inhibition efficiencies on mild steel electrodes increased with increase in gum exudate concentrations up to 300 ppm, corresponding to the inhibition efficiency of about 43% and its inhibition efficiency increased up to 81.6% with addition of halide ions due to synergistic effects. The enhancement effect of the halide ions was higher with iodide than with bromide ions. The synergism parameter, S1, evaluated was greater than unity, consistent with synergistic effect. The adsorption of Acacia senegal gum on the mild steel surface obeyed Langmuir’s adsorption isotherm. The results obtained, i.e., corrosion rates of mild steel, inhibition efficiencies of Acacia senegal gum exudates and the synergistic effects of Acacia senegal gum exudates and halides from polarization and impedance measurements were in good agreement.</p> <p><strong>Keywords</strong>: corrosion, inhibition, mild steel, synergistic effect, Acacia senegal, gum exudate</p> Jovine Emmanuel Joseph Buchweishaija Copyright (c) 2021 2021-05-19 2021-05-19 47 2 686 697 10.4314/tjs.v47i2.24 Application of optimal control to tuberculosis model with parameter estimations: Bayesian approach https://www.ajol.info/index.php/tjs/article/view/207372 <p>In this paper, one-strain tuberculosis (TB) model with two control mechanisms, education campaigns and chemoprophylaxis of TB-infected patients, was studied to determine their effects on the reduction of latent and active TB cases. In the case of analysis, boundedness and positivity of the model solutions were carried out to determine the biological feasibility of the study. Besides, the calibration of the parameters by utilizing the identifiability technique through the Markov chain Monte Carlo (MCMC) was thoroughly analysed. The optimum conditions for controlling TB were derived from the Pontryagin Maximum Principle. The numerical simulations were carried out using the forward-back sweep method with the help of the Runge-Kutta fourth-order numerical schemes. Simulation results showed that the education campaigns strategy is more effective in reducing TB infections than the chemoprophylaxis of TB-infected individuals. The combination of the two control strategies reduces a significant number of infections than when each strategy is used on its own. To minimize the transmission of TB from the community, we recommend the education campaigns strategy be a focal point and treatment of latent TB to be paired with the treatment of active TB cases.</p> <p><strong>Keywords</strong>: Tuberculosis, Education campaigns, Chemoprophylaxis, MCMC</p> Goodluck M Mlay Alfred K Hugo Copyright (c) 2021 2021-05-19 2021-05-19 47 2 698 709 10.4314/tjs.v47i2.25 Application of linguistic/non-numeric fuzzy aggregation to the ranking of processed crops https://www.ajol.info/index.php/tjs/article/view/207481 <p>A non-numeric fuzzy aggregation approach is applied for the fusion of information obtained from farmers and experts for evaluation and selection of alternatives under multiple criteria. The technique has the ability to assign linguistic variable to fused information and find consensus of gathered opinions from a number of experts on crop processing for each processed crop. The technique is illustrated with a crop processing problem by adding value to the crop and increase income to entrepreneurs. The proposed technique has been successfully applied to the ranking of the processed crops based on the expert’s opinions, thus obtaining best preferences based on product, technology, marketing, and customer satisfaction. Five crops, namely beans, maize, rosella, sunflower and rice were ranked. Out of the five ranked crops, two processed crops (maize and sunflower) obtained high ranking.</p> <p><strong>Keywords</strong>: Linguistic variables, Fuzzy aggregation, Processed crops, Decision making</p> David Koloseni Copyright (c) 2021 2021-05-22 2021-05-22 47 2 710 717 10.4314/tjs.v47i2.26 Levels of selected toxic and essential elements in fish and oysters from Western Indian Ocean, Coast of Tanzania https://www.ajol.info/index.php/tjs/article/view/207482 <p>Concentrations of toxic and essential elements in selected finfish and shellfish collected from Dar es Salaam and Tanga, Indian Ocean coast of Tanzania are presented. The elemental concentrations were determined using Energy Dispersive X-ray Fluorescence (EDXRF) spectrometer coupled with X-lab ProTM software. The mean concentrations of metals observed in finfish and shellfish collected from Tanga ranged from 3.40–5.75, 1.8–37.17, 3.5–7.1, 0.6–1.3, 0.53–0.73 and 16.80–96.70 mg kg–1 for As, Cu, Mn, Ni, Pb and Zn, respectively. For Dar es Salaam, the mean concentrations of metals ranged from 3.34–9.46, 2.90–30.53, 3.4–6.9, 0.7–1.0, 0.57–0.80 and 14.2–100.90 mg kg–1 for As, Cu, Mn, Ni, Pb and Zn, respectively. Thumbprint emperor showed the highest levels of Cu and Ni; octopus showed the highest values of As and Pb, while sardines showed the highest level of Mn. Oysters, used as pollution indicators in this study showed the highest elemental concentrations and exceeded their mean levels in finfish from Dar es Salaam by factors of 1.30, 7.15, 6.27, 2.72, 1.29 and 35.57 for As, Cu, Mn, Ni, Pb and Zn, respectively. In samples from Tanga, the metal concentrations in oysters were several times higher (3.76, 17.68, 1.12, 3.89, 1.88 and 66.92 for As, Cu, Mn, Ni, Pb and Zn) than in finfish, respectively. Based on metal concentrations in oysters, it can be concluded that coastal waters are contaminated with heavy metals. However, with an exception of arsenic and copper, the elemental levels in finfish are within the maximum permissible levels recommended by various international standards and guidelines.</p> <p><strong>Keywords</strong>: Finfish, toxic elements, essential elements, pollution, EDXRF</p> Daniel A Shilla Shovi F Sawe Copyright (c) 2021 2021-05-22 2021-05-22 47 2 718 727 10.4314/tjs.v47i2.27 Mathematical analysis of harvested predator-prey system with prey refuge and intraspecific competition https://www.ajol.info/index.php/tjs/article/view/207483 <p>In this paper, a predator-prey relationship in the presence of prey refuge was studied. The analysis of the dependence of locally stable equilibrium points on the parameters of the problem was carried out. Bifurcation and limit cycles for the model were analyzed to show the dynamical behaviour of the system. The results showed that the system is stable at a constant prey refuge m = 0.3 and prey harvesting rate H = 0.3. However, increasing m and decreasing H or vice versa, the predator-prey system remains stable. It was further observed that for a constant prey refuge m ≥ 0.78, the predator population undergoes extinction. Therefore, m was found to be a bifurcation parameter and m = 0.78 is a bifurcation value.</p> <p><strong>Keywords</strong>: Prey refuge, bifurcation, harvesting, intraspecific competition, phase portrait</p> Alanus Mapunda Thadei Sagamiko Copyright (c) 2021 2021-05-22 2021-05-22 47 2 728 737 10.4314/tjs.v47i2.28 Determination of 40K, 226Ra and 228Ra concentrations with dose rates in crayfish from Ode Omi River and radiological implications to the consumers https://www.ajol.info/index.php/tjs/article/view/207484 <p>Natural radionuclides such as <sup>40</sup>K, <sup>226</sup>Ra and <sup>228</sup>Ra are found naturally in water and sediments of rivers, likewise in soils. They are transferred to aquatic animals through ingestion. Radioactivity concentrations and dose rates of <sup>40</sup>K, <sup>226</sup>Ra and <sup>228</sup>Ra in crayfish species from Ode Omi River in coastal region, Ogun State Southwest of Nigeria were determined by gamma spectrometry using NaI (TI) detector coupled with a pre-amplifier base to a multiple channel analyzer (MCA). 15 samples of crayfish were collected. Cherax tenuimanus had the highest mean concentration and dose rate of values 106.87 ± 9.11 Bq kg<sup>–1</sup> and 0.00960 mGy hr<sup>–1</sup> respectively for <sup>40</sup>K. Moreso, for <sup>226</sup>Ra, Cherax quadricarinatus had the highest mean concentration and dose rate of values 2.57 ± 0.82 Bq kg–1 and 4.50 x 10–7 mGy hr<sup>–1</sup> respectively. Concerning228Ra, Astacopsis gouldi had the highest mean concentration and dose rate of values 5.23 ± 0.46 Bq kg–1 and 5.86 x 10–13 mGy hr<sup>–1</sup>, respectively. The average dose rate of the radionuclides in all the crayfish was calculated to be 4.62 x 10 ̶ 3 mGy hr<sup>–1</sup> which was below the 0.4 mGy hr<sup>–1</sup> limit recommended. The average annual committed effective dose and average excess lifetime cancer risk of all the radionuclides to the consumers were 0.0807 mSv yr<sup>–1</sup> and 0.589 x 10<sup>–4</sup>, respectively, which were below global limits of 1.0 mSv yr<sup>–1</sup> and 0.29 x 10<sup>–3</sup>, respectively, therefore, the ingestion of these natural radionuclides could not pose any radiological health hazards to the aquatic animals, likewise man the consumers.</p> <p><strong>Keywords</strong>: Radionuclide concentration, Dose rate, Cancer Risk.</p> Olusegun Sowole Qasim Abolanle Adeniji Muyideen O Olagunju Copyright (c) 2021 2021-05-22 2021-05-22 47 2 738 744 10.4314/tjs.v47i2.29 Synthesis and antimicrobial activities of some new sulfonyl phenoxides https://www.ajol.info/index.php/tjs/article/view/207485 <p>Four new sulfonyl phenoxides were synthesized through O-sulfonylation reaction of phenolic compounds with 5-chloro-1-ethyl-2-methylimidazole-4-sulfonyl chloride in good yield. FT-IR, 1H-NMR, 13C-NMR, and DEPT 135 NMR were carried out to characterize and the thin layer chromatography (TLC) confirm the purity. Antimicrobial activities of the sulfonyl phenoxides against Gram-positive (methicillin-susceptible <em>Staphylococcus aureus</em>, methicillin-resistant <em>Staphylococcus aureus</em>, and <em>Bacillus subtilis</em>), Gram-negative (<em>Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae</em>), and <em>Candida albicans</em> were carried out using the standard microbiological method. The antimicrobial activities were referenced to ciprofloxacin and itraconazole, antibacterial and antifungal drug respectively. The in vitro antimicrobial studies of 5-chloro-1-ethyl-2-methyl-1H-imidazole-4-sulfonyl(4-chloro-3-methyl)phenoxide and 5-chloro-1-ethyl-2-methyl-1H-imidazole-4-sulfonyl-2-methylphenoxide showed moderate activity against <em>C. albicans</em>. The four sulfonyl phenoxides had weak activities against Gram-positive and Gram-negative bacteria.</p> <p><strong>Keywords</strong>: Sulfonyl phenoxides, Antimicrobial, Phenolic compounds, O-Sulfonylation reaction</p> Oluwaseyi B Ovonramwen Bodunde J Owolabi Abiodun Falodun Copyright (c) 2021 2021-05-22 2021-05-22 47 2 745 753 10.4314/tjs.v47i2.30 Integration of geophysics and remote sensing techniques in mapping zones mineralised with disseminated gold and sulphide minerals in Lolgorien, Narok County, Kenya https://www.ajol.info/index.php/tjs/article/view/207486 <p>Even though ground geophysical surveys (especially Induced polarization and resistivity) are applied in mineral exploration, their effectiveness in identification of mineralised zones is often enhanced by integrating other mineral exploration techniques such as remote sensing and geological investigations. Integrating different techniques helps in reducing uncertainty that is often associated with mineral exploration. The methods being integrated also depend on characteristics of mineralisation and those of host rock. In this study, geophysical survey methods (induced polarization and resistivity) were integrated with remote sensing and geological methods to delineate mineralised zones in Lolgorien beyond reasonable doubt. By integrating these methods, it was found that Lolgorien’s gold and sulphide minerals (disseminated minerals) are hosted in massive quartz veins and auriferous quartz veins hosted in Banded Iron Formations. It was also found that this mineralisation was controlled by faults which mainly trend in two directions (NW-SE) and (NE-SW).</p> <p><strong>Keywords</strong>: hydrothermal alteration, chargeability, resistivity, band ratio, lineament density</p> Sammy O Ombiro Akinade S Olatunji Eliud M Mathu Taiwo R Ajayi Copyright (c) 2021 2021-05-22 2021-05-22 47 2 754 768 10.4314/tjs.v47i2.31 Sign language recognition using Kinect sensor based on color stream and skeleton points https://www.ajol.info/index.php/tjs/article/view/207662 <p>This paper presents a sign language recognition system based on color stream and skeleton points. Several approaches have been established to address sign language recognition problems. However, most of the previous approaches still have poor recognition accuracy. The proposed approach uses Kinect sensor based on color stream and skeleton points from the depth stream to improved recognition accuracy. Techniques within this approach use hand trajectories and hand shapes in combating sign recognition challenges. Therefore, for a particular sign a representative feature vector is extracted, which consists of hand trajectories and hand shapes. A sparse dictionary learning algorithm, Label Consistent K-SVD (LC-KSVD) is applied to obtain a discriminative dictionary. Based on that, the system was further developed to a new classification approach for better results. The proposed system was fairly evaluated based on 21 sign words including one-handed signs and two-handed signs. It was observed that the proposed system gets high recognition accuracy of 98.25%, and obtained an average accuracy of 95.34% for signer independent recognition.</p> <p><strong>Keywords: </strong>Sign language, Color stream, Skeleton points, Kinect sensor, Discriminative dictionary.</p> Isack Bulugu Copyright (c) 2021 2021-05-26 2021-05-26 47 2 769 778 10.4314/tjs.v47i2.32 Evaluation of scatter suppression algorithm for X-ray exposure of soft tissue equivalent phantoms over nominal energy range using FLUKA code https://www.ajol.info/index.php/tjs/article/view/207664 <p>Soft tissue imaging is heavily impaired by streaks and cupping effects associated with X-ray scatter. Quality of images from projection imaging may be improved by the use of enhanced anti-scatter grids’ designs with potency to reject significant scatter. However, optimization of grid characteristics requires investigation to improve diagnostic image quality. Transmitted scatter spatially distributed degrades images engendering need for effective scatter correction protocols. This study investigated the pre-scan scatter suppression algorithm for X-ray exposure of soft tissue equivalent phantoms over nominal energy range. Adipose tissue and polymethyl methacrylate phantoms of cross-sectional area (30 x 30) cm<sup>2</sup> and of varying thickness from 2 to 8 cm in 1 cm increments were successively exposed using energy ranging between 20–50 kVp. Monte Carlo simulation based on FLUKA code and flair interface was used to generate an input file for execution. The source simulated five cycles of ten million photons each of annular X-ray photon beam of radius, r = 0.5 cm at fixed field of view (FOV) through anti-scatter grid on to gadolinium oxysulfide detector. The transmitted total, scatter and primary estimates were evaluated with and without grids over varying phantom thicknesses, energy and grid design features. The simulated and experimental results obtained were comparable and in agreement with previous literature. Pearson’s correlation coefficients for scatter fraction and scatter to primary ratio were 0.983 and 0.981, respectively. The strong correlation between simulation and experiment results indicated correctness in methodology and protocol. The algorithms and protocols in the simulation would be appropriate for designing grids with enhanced scatter rejection capabilities.</p> <p><strong>Keywords:</strong> FLUKA code, Monte Carlo simulation, Scatter suppression algorithm, Scatter correction, X-ray imaging systems.</p> <p>&nbsp;</p> Samson O Omondi Innocent J Lugendo Ramadhan R Kazema Robert Kinyua Copyright (c) 2021 2021-05-26 2021-05-26 47 2 779 789 10.4314/tjs.v47i2.33 Influence of carbonitriding conditions on phase composition and residual stresses for 20MnCr5 low alloy steel https://www.ajol.info/index.php/tjs/article/view/207669 <p>This paper reports an investigation of the influence of carbonitriding conditions for 20MnCr5 low alloy steel. Three gaseous carbonitriding conditions were investigated based on different carbon and nitrogen potentials to attain varying levels of carbon between 0.62 and 0.93% mass, whereas for nitrogen between 0.19 and 0.26% mass at the surface. Analysis of retained austenite and residual stress distributions was conducted using X-ray diffraction technique. The effective case depth varied between 900 and 1200 µm. The case microstructures were characterized by varying proportions of retained austenite and martensite, while the core contained essentially bainitic microstructures. The maximum amount of retained austenite which occurred at a depth of 50 µm from the subsurface ranged between 30 and 70% mass and significantly influenced the level of surface micro-hardness whereas the core hardness remaining relatively constant at 450 HV1. High values of residual stresses in martensite phase were observed. The signs, magnitudes, distributions and location of maximum compressive residual stresses were highly influenced by the maximum fraction of retained austenite. Retained austenite of 30%, 50% and 70% mass at the surface lead to peak compressive residue stresses of -280, -227, and -202 MPa at depths of 555, 704, and 890 μm, respectively.</p> <p><strong>Keywords:</strong> Carbonitriding, retained austenite, martensite, residual stress, XRD.</p> Richard J Katemi Jeremy Epp Copyright (c) 2021 2021-05-26 2021-05-26 47 2 790 799 10.4314/tjs.v47i2.34 Assessment of the quality and quantity of organic matter in the Rufiji mangrove surface sediments using biochemical composition https://www.ajol.info/index.php/tjs/article/view/208720 <p>This study was carried out to investigate spatial changes in the quality and quantity of sedimentary organic matter in the Rufiji mangrove system, Tanzania. Sediment samples were collected from three sampling sites. Total organic matter in mangrove sediments ranged from 7.28 ± 2.02% to 10.58 ± 1.34%. Protein concentrations varied from 1,145.33 ± 20.33 μg/g to 2,747.50 ± 25.14 μg/g in the mangrove sediments. Total carbohydrates, lipids and biopolymeric carbon in mangrove sediments ranged between 1,110.50 ± 16.31 μg/g and 1,914.17 ± 27.79 μg/g, 1,436.50 ± 24.13 μg/g and 6,373.50 ± 25.79 μg/g, and 4,496 μg C/g and 10,231.50 μg C/g, respectively. Tannins and lignins in mangrove sediments varied from 817.67 ± 12.97 μg/g to 1786.50 ± 30.74 μg/g, while stable carbon isotope (δ<sup>13</sup>C) in Rufiji mangrove sediments ranged between –26.64 ± 0.10 ‰ and –25.48 ± 0.13 ‰. Higher protein:carbohydrate (PRT:CHO) at station 3 indicated the presence of freshly deposited organic matter. The high lipid:carbohydrate (LPD:CHO) ratios observed in the Rufiji mangrove systems pointed towards the high quality of labile organic matter which supports benthic fauna. PCA revealed the association of variables and their distribution on trends across sites of the Rufiji mangrove system.</p> <p><strong>Keywords</strong>: Organic matter, biochemical composition, Rufiji, mangroves, sediments</p> <p>&nbsp;</p> Daniel A. Shilla Copyright (c) 2021 2021-06-15 2021-06-15 47 2 800 811 10.4314/tjs.v47i2.35 Biodiesel production by esterification of ricinoleic acid over a series of synthesized sulfated zirconia catalysts https://www.ajol.info/index.php/tjs/article/view/209087 <p>A series of sulfated zirconia (SZ) were synthesized and evaluated for catalytic esterification of ricinoleic acid obtained from the castor oil with butanol at 110 °C. The effect of alcohols’ chain length was studied using butanol (C4), propanol (C3), ethanol (C2) and methanol (C1) at 65 °C, and reflux of corresponding alcohol boiling points. The synthesized catalysts were characterized using nitrogen porosimetry, X-ray powder diffraction, thermogravimetric analysis and Diffuse Reflectance Infrared Fourier Transform Spectroscopy. Analysis of ricinoleic conversion was performed using gas chromatography. Sulfuric acid loading improved the surface area of zirconia at a lower dose. The surface areas of the catalysts increased as the concentrations of sulfuric acid solution were increased from 0.025 to 0.10 M, after which the decline was observed. SZ obtained at 0.05 M H<sub>2</sub>SO<sub>4</sub> (0.05SZ) gave the optimal catalytic activity compared to the other series of SZ used. The ricinoleic acid conversion decreased with increase of alcohol alkyl chain from C1-C4 at 65 °C, but increased under the reflux temperature of the corresponding alcohols, with the maximum conversion being 47% at 118 °C for the reaction involving butanol. Overall, the synthesized SZ catalysts are deployable in biodiesel production from castor oil upon optimizing other conditions.</p> <p><strong>Keywords</strong>: Ricinoleic acid; Sulfated zirconia; Biodiesel production</p> Elianaso Elimbinzi Stephen Nyandoro Copyright (c) 2021 2021-05-31 2021-05-31 47 2 812 825 10.4314/tjs.v47i2.36 Probabilistic seismic hazard assessment and site analyses of Arusha International Conference Centre (AICC), Arusha, Tanzania https://www.ajol.info/index.php/tjs/article/view/209088 <p>This work presents the evaluation of earthquake resistance of the Arusha International Conference<br>Centre (AICC) complex, in Tanzania. The evaluation included probabilistic seismic hazard<br>analysis (PSHA) and site response analysis. Seismic sources considered to constitute a seismic<br>hazard in this study were randomly occurring seismicity located within five tectonic provinces<br>around the site. For each province the seismic hazard is based on a cursory analysis of earthquake<br>data from compiled ESARSWG bulletins and temporary deployed networks within the North<br>Tanzania Divergence (NTD). Bedrock response signal together with the information of material<br>characteristics from boreholes around the AICC site were used in analysis of site response. PSHA<br>results indicated uniform hazard spectra values of 0.15, 0.2 and 0.27 g for return periods of 475,<br>975 and 2475 years, respectively. The surface ground response results indicated a maximum<br>amplification factor of 3.7 and a spectral response of 4.5 g for a wave period of 0.6 sec that<br>matches the natural frequency of the 6-7 storey buildings of the AICC complex. It is this<br>resonance effect on the buildings that is assumed to have caused intense shaking in the earthquake<br>of December 5th 2005 from Lake Tanganyika.</p> <p><strong>Keywords</strong>: Probabilistic seismic hazard analysis; Arusha International Conference Centre; East<br>African Rift System; Uniform hazard spectra; Site effect.</p> Richard W Ferdinand Copyright (c) 2021 2021-05-31 2021-05-31 47 2 826 840 10.4314/tjs.v47i2.37 Variations in the effects caused by magnetic field on chlorophyll, nitrogen, calcium, and iron contents in species of vegetable plants https://www.ajol.info/index.php/tjs/article/view/209089 <p>The rates of reduction in chlorophyll and nutrients such as nitrogen, calcium and iron with the distance or range of source of Magnetic Field (MF) had not been considered. In this work, patterns of damage or reduction caused by a magnetic field on two different species of vegetables were studied. The first group was planted in an environment without the influence of MF, while the second group was subjected to high MF under the 330 kV electric lines. The magnetometer was used to measure the MF intensities. The chlorophyll content of each vegetable sample was determined on the field with a portable chlorophyll meter. The dried harvested samples of two different vegetable species were analyzed using an Atomic Absorption Spectrophotometer (AAS) to assess the concentrations of nitrogen (N), calcium (Ca), and iron (Fe) in the samples. Results of elemental concentrations were subjected to statistical analysis to appraise the relationships between the measured variables as responses to high MF. It was observed that the effects of high MF are stronger on spinach vegetable than Lagos spinach. This suggested that the effects of MF on plants are not only MF intensity dependent, but also species-dependent.</p> <p><strong>Keywords</strong>: Magnetic field; Exposure; Regression analysis; Power transmission; Chlorophyll; Iron</p> Olusegun O Alabi Samuel O Sedara Kafayat Adeyemi Felix Oladejo Mutiu A Fakunle Funmilayo Ayedun Copyright (c) 2021 2021-05-31 2021-05-31 47 2 841 846 10.4314/tjs.v47i2.38 Investigation of some factors associated with utilization of maternal health care services by adolescent mothers in Tanzania https://www.ajol.info/index.php/tjs/article/view/209495 <p>This study examined some factors associated with the utilization of maternal health care services<br>by adolescent mothers (15-19 years) in Tanzania in order to provide advice accordingly. The study<br>used cross-sectional study of adolescent mothers aged 15-19 years using Demographic Health<br>Survey and Malaria indicator Survey 2015/16 data. The dependent variables were number of<br>antenatal care visits, the place where an adolescent mother delivered and post-natal checkup<br>(adolescent mother’s health checking after being discharged or after a home delivery). The<br>independent variables were birth order, education level of a mother, marital status of a mother,<br>media exposure, wealth index, distance to health facility. Multiple binary logistic regression was<br>used to examine an association between each dependent variable and their respective independent<br>variables. Data was analyzed using IBM SPSS statistics and STATA. This study used 550<br>adolescent mothers in the analysis. Majority of the adolescent mothers had less than four Antenatal<br>Care (ANC) visits (53.5%), while 68.5% of adolescent mothers delivered at a health facility.<br>Adolescent mothers with two or more children had less odds of having at least four ANCs<br>compared to those with one child, whereas adolescent mothers with at least secondary education<br>had greater odds of delivering at a health facility compared to those who had no education.<br>Adolescent mothers who had at least four antenatal care visits and those who are married had<br>greater odds of checking their health after being discharged compared to adolescent mothers who<br>had less than 4 ANCs and single adolescent mothers. It was advised that provision of maternal<br>education to young girls on the importance of safe delivery and health checking after delivery is<br>very important to reduce adolescent maternal morbidity and mortality in the country.</p> <p><strong>Keywords</strong>: Adolescent; Maternal Health; Logistic regression; Chi-square</p> Elia Magwaja Jacqueline Minja Majige Selemani Budeba Rocky R.J. Akarro Copyright (c) 2021 2021-06-26 2021-06-26 47 2 847 861 10.4314/tjs.v47i2.39 Probabilistic seismic hazard analysis for Northern Tanzania Divergence Region and the adjoining areas https://www.ajol.info/index.php/tjs/article/view/209723 <p>This paper presents the seismic hazard levels for the Northern Tanzania Divergence (NTD) and adjoining areas by using area seismic source zones. The 15 source zones were considered based on the major geological and tectonic features, faulting style, and seismicity trends. For each source, earthquake recurrence parameters were computed by using the earthquake catalogue with events compiled from 1956 to 2011. The peak ground accelerations (PGA) and spectral accelerations (SA) at 0.2 and 2.0 second, respectively, were computed for a 10% probability of exceedance in 50 years at sites defined by a 0.1° x 0.1° grid. The recurrence parameters of 15 zones and attenuation relations developed by Akkar et al. (2014) and Chiou and Youngs (2014) were integrated into a logic tree. Obtained results that are presented as hazard maps show strong spatial variations ranging from 60 to 330 cm/s/s for PGA, from 100 to 650 cm/s/s at 0.2 sec and from 6 to 27 cm/s/s at 2 sec for 475 years mean return period and 5% damping. Hazard levels depict the general tectonic setting of the study area with the western (Eyasi-Wembere) and central (Natron-Manyara-Balangida) rift segments having relatively high PGA values compared with the eastern Pangani rift. This work provides indications of seismic hazards to policymakers and planners during planning and guidelines for earthquake-resistant design engineers.</p> <p><strong>Keywords</strong>: Homogeneous Earthquakes Catalogue; GMPE; PSHA; NTD</p> Michael M Msabi Richard W Ferdinand Copyright (c) 2021 2021-05-31 2021-05-31 47 2 862 876 10.4314/tjs.v47i2.40