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> Geometric Morphometric Comparison of Abu Mullet, Planiliza abu (Heckel, 1843) Populations in Bushehr Basin, Iran https://www.ajol.info/index.php/tjs/article/view/203166 <p>Many fish behavior and habitats could be defined based on the fish morphology, thus, using the fish body shape, in addition to its genetic characteristics, could be used to infer the type of fish habitat and its characteristics. This study aimed to compare the body shapes of five populations of abu mullet, <em>Planiliza abu</em> (Heckel, 1843), in Bushehr basin using geometric morphometric method. Some 162 specimens from Hendijan, Genaveh, Helleh, Kaki and Mond rivers were used. Three morphometric characters, total length (TL), fork length (FL) and standard length (SL) were measured. Samples were photographed from the left side, then 18 landmarks were digitized using ImageJ software. Data obtained from Procrustes were analyzed by multivariate analysis using PCA and CVA. The results of PCA analysis showed significant differences between Kaki and other populations (P &lt; 0.0001). The CVA analysis of the studied populations showed that the highest Mahalanobis and Procrustes distance was between the Hendijan and Kaki populations. The major differences observed were in head length, body height, caudal peduncle length, dorsal and pelvic fins position. It seems that the Hendijan and Kaki populations are distinct from others that might be due to environmental or genetic differences which could be cleared by molecular analysis.</p> <p><strong>Keywords</strong>: Geometric morphometry; Landmark; Morphological properties; Procrustes analysis</p> Fatemeh Shabaninejad Yazdan Keivany Dara Bagheri Copyright (c) 2021 2021-02-14 2021-02-14 47 1 1 9 10.4314/tjs.v47i1. Perceived Risk Factors of Dysmenorrhea among Female Undergraduates in University of Ilorin, Ilorin, Nigeria https://www.ajol.info/index.php/tjs/article/view/203370 <p>Dysmenorrrhea is one of the leading causes of school absenteeism among female undergraduates in University of Ilorin, Nigeria. Therefore, the study investigated the perceived risk factors of dysmenorrhea among female undergraduates in the University of Ilorin, Nigeria. Descriptive research design of survey type was used for the study. Population for this study comprised of female undergraduates in the University of Ilorin for 2018/2019 academic session. Multi-stage sampling technique of simple, proportionate, purposive and convenience sampling techniques were used to select 263 respondents that participated in the study. The researcher developed a questionnaire which was validated by 3 experts from the field of health educator and community medicine was used for the study. Degree of consistency of the instrument used for the study was confirmed through test-re-test approach and result of r = 0.82 obtained. Non-parametric statistics of Chi-square was used to test the hypotheses formulated for the study at 0.05 alpha level. The findings of the study indicated that stress and high intake of sugar were risk factors for dysmenorrhea among female undergraduates in the University of Ilorin (Chi- square value of 83.45, p = 0.000 with 9 df, (Chi- square value of 64.06, p = 0.001 with 9 df). The researchers concluded that the inability to manage stress among female undergraduates and high intake of foods containing excessive sugar were risk factors of dysmenorrhea among female undergraduates at the University of Ilorin. The researchers recommended that the school authority management should organize stress seminars and campaigns to help address stress problems experienced by female undergraduates in the University of Ilorin. Also, the university authority should organize enlightenment campaigns that will educate undergraduates on the risks involved in the consumption of unhealthy foods which contain excessive sugar such as biscuits or snacks to reduce pains experienced by female undergraduates in the University of Ilorin, during the menstrual period.</p> <p><strong>Keywords</strong>: Risk Factors; Dysmenorrhea; Stress; Female; Undergraduates</p> <p>&nbsp;</p> Ibrahim Ologele Precious Daniel Oyiza Ogunsola Mufutau Tijani Copyright (c) 2021 2021-02-14 2021-02-14 47 1 10 18 10.4314/tjs.v47i1. Wastewater Clarification and Microbial Load Reduction Using Agro-Forestry and Agricultural Wastes https://www.ajol.info/index.php/tjs/article/view/203371 <p>Five agro-wastes, namely: cassava peels, Irish potato peels, <em>Jatropha curcas</em> seeds, <em>Moringa oleifera</em> seeds and rice husks were investigated as plant-based coagulants for turbidity and microbial load removal from sewage wastewater. <em>Moringa oleifera</em> and <em>Jatropha curcas</em> seeds before usage were defatted with 95% ethanol and the active coagulating component was extracted with 1.0 M NaCl. For the other three agro-wastes, their ashes were evaluated for turbidity and microbial load removal. The ash was prepared through pyrolysis of the raw biomass at a temperature of 800 °C for 3 h. The effect of pH, coagulant dose, settling time on turbidity reduction was investigated using sewage wastewater with an initial turbidity of 464.11 ± 0.13 NTU. The microbial load removal of the coagulants was investigated using three media onto which 1 mL of treated wastewater was poured and streaks were made using sterile swabs and then incubated at 37 °C for 24 h. <em>Jatropha curcas</em> and rice husks ashes exhibited the maximum turbidity reduction of 97.0% and 95.0%, respectively at pH 2, whereas for <em>Moringa oleifera</em>, the highest turbidity removal (96.0%) was achieved between pH 6 and 10. Additionally, it was observed that the electrical conductivity and total dissolved solids of the clarified wastewater increased as the doses were increased for all coagulants due to inorganic salts contained in seeds. The microbial load understudy was successfully reduced in wastewater clarified with <em>Jatropha curcas</em> and rice husks ashes, contrary to <em>Moringa oleifera</em> that increased microbial load content. The raw biomass and ashes for cassava and Irish potato peels could not clarify sewage wastewater. The results from this study have demonstrated that plant-based materials used performed effectively in turbidity and bacteria removal from sewage wastewater.</p> <p><strong>Keywords</strong>: Domestic Wastewater; Clarification; Agro-Wastes; Turbidity; Microbial Load</p> Joel Njewa Ephraim Vunain Timothy Biswick Copyright (c) 2021 2021-02-14 2021-02-14 47 1 19 33 10.4314/tjs.v47i1. Characterization, Antimicrobial and Toxicity Studies of Silver Nanoparticles Using Opuntia ficus indica Leaves Extracts from Effurun, Delta State https://www.ajol.info/index.php/tjs/article/view/203372 <p>The silver nanoparticles were synthesized by reacting silver nitrate, a metal precursor with the extract obtained from the leaves of <em>Opuntia ficus</em> indica, which acts as a reducing and stabilizing agent. Formation of silver nanoparticles was indicated by colour change from light yellow to dark brown which was confirmed by ultraviolet-visible (UV-Vis) spectroscopy showing surface plasmon band at 369 nm resulting from relatively small amount of reductive biomolecules for the silver ion reduction. Scanning electron microscope (SEM) analysis gave the morphology of the nanoparticles and showed that the silver particles were of spherical shape. Fourier transform infrared (FTIR) spectrometer presented the functional groups and it showed that the reduction of silver was as a result of the presence of the absorption band of -OH stretching of alcohols in biomolecules such as glycosides, terpenoids, phenols, and alkaloids which made capping and stability of the particles. The antimicrobial activities of silver nanoparticles were determined using agar well diffusion method with some clinical pathogenic microbes such as methicillin resistant <em>Staphylococcus aureus, </em>vanocomycin resistant <em>Enterococci, Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, Klebsiella pneumonia, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhi, Candida albicans, Candida krusei, Candida stellatoidea</em> and <em>Candida tropicalis</em>. High anti-microbial activities were seen in <em>Pseudomonas aeruginosa</em> and methicillin resistant <em>Staphylococcus aureus</em> having zone of inhibition of 30 mm and 29 mm with minimum inhibitory concentration (MIC) value of 1.25 mg/L and minimum bactericidal concentration (MBC) value of 2.5 mg/L, respectively. Toxicity study revealed that the silver nanoparticles were not toxic at 100 mg/L indicating that it is eco-friendly.</p> <p><strong>Keywords</strong>: Characterization; Antimicrobial; Toxicity; Silver nanoparticles; <em>Opuntia ficus indica</em>.</p> Christiana Ogwuche Harrison Moses Copyright (c) 2021 2021-02-14 2021-02-14 47 1 34 46 10.4314/tjs.v47i1. Potential of Fungi Isolated from Diesel Contaminated Soil to Degrade Diesel https://www.ajol.info/index.php/tjs/article/view/203374 <p>Diesel is a complex mixture and a common pollutant, consisting mainly of aliphatic hydrocarbons ranging from C9 to C23 and a number of aromatic compounds. The main purpose of this study was to isolate fungi from diesel contaminated soil for biodegradation of diesel contaminated soil. Two fungal species (<em>Aspergillus flavus</em> and <em>Saccharomyces cerevisiae</em>) were isolated from a diesel contaminated site using cultural and biochemical characterisation. The isolates were screened for their ability to utilize diesel as carbon source. The biodegradation rate of the fungi isolated was measured by determining the optical density using spectrophotometry. The fungal isolates were further tested for utilisation of hydrocarbons using mineral salt medium (MSM) supplemented with diesel in varying concentrations (1%, 2%, 5% and 10%). The optimum pH for biodegradation (4, 6 and 8) was determined. Both isolates degraded best at 5% diesel concentration with optical densities of 1.751 and 1.546 for <em>A. flavus</em> and S<em>. cerevisiae</em>, respectively. The optimum pH for <em>A. flavus</em> was pH 8 (optical density 1.390), while the optimum pH for <em>S. cerevisiae</em> was pH 6 (optical density 1.234). The results of this study showed that the isolates were able to degrade 5% diesel concentration at optimum pH of 8, and can be developed to remediate diesel contaminated environment.</p> <p><strong>Keywords</strong>: Diesel; biodegradation; <em>Aspergillus flavus</em>; <em>Saccharomyces cerevisiae</em></p> Oluwafemi Oyewole Ramat Raji Suzan Okeke Innocent Musa Gift Chukwuma Japhet Yakubu Copyright (c) 2021 2021-02-14 2021-02-14 47 1 47 56 10.4314/tjs.v47i1. Isolation and Quantification of Flavonoids from Kigelia africana (Lam.) Benth Fruit and Bark and their Antiradical and Antibacterial Activities https://www.ajol.info/index.php/tjs/article/view/203419 <p><em>Kigelia africana</em> is an evergreen deciduous tree used in Zimbabwe folklore medicine for wound and diabetes ulcers healing. This paper reports the isolation and quantification of flavonoids from stem barks and fruits of <em>K. africana</em> as well as their antibacterial and antiradical activities. Flavonoids in ethanol and ethyl-acetate extracts were quantified using UV-Vis spectrophotometry and were found to be 213.490 ± 0.001 mg/L and 36.614 ± 0.001 mg/L, respectively per quercetin equivalent. The preparative and analytical thin layer chromatography was used to profile the flavonoids from fruits and barks using ethyl-acetate and petroleum ether (3:7 v/v) mobile solvent systems. Ethanol extract yielded three flavonoids with Rf values of 0.05; 0.79 and 0.93, while the ethyl-acetate extract yielded two flavonoids with Rf values of 0.21 and 0.73. The antiradical activities of the extracts were determined using DPPH radical scavenging method using quercetin as reference, and the activities were found to be over 80% at 150 mg/L. The disc diffusion method was used for antibacterial activity determination, and flavonoids from both ethanol and ethyl-acetate extracts showed zones of inhibition ranging from 0 to 22 mm against <em>Staphylococcus aureus</em> and <em>Pseudomonas aeruginosa</em>. Although the present study revealed that flavonoids from <em>K. africana</em> possess significant antibacterial and antioxidant activities, more studies are necessary for them to be incorporated in polyherbal formulations for wound and diabetic ulcer topical treatments.</p> <p><strong>Keywords</strong>: Diabetic foot ulcers; <em>Kigelia africana</em>; Antibacterial activity; Flavonoids; Antioxidant activity.</p> Pamhidzai Dzomba George Mhini Copyright (c) 2021 2021-02-14 2021-02-14 47 1 57 69 10.4314/tjs.v47i1. Influence of COVID-19 on the Psychological Wellbeing of Tertiary Institution Students in Nigeria https://www.ajol.info/index.php/tjs/article/view/203422 <p>The outbreak of COVID-19 has led to a global lockdown, pending the time medical researchers find a vaccine for the coronavirus. This study examined if loneliness, depression and stress are influences of COVID-19 on the psychological wellbeing of tertiary institutions students in Nigeria. A descriptive research design of survey type was employed for this study. The population comprised all students of tertiary institutions in Nigeria totaling about 4,406,000. One hundred and thirty-seven (137) respondents were sampled for the study. A validated researcher developed questionnaire tested for reliability was used for the study. The data collected were analyzed using descriptive statistics. Chi-square was used to test the hypotheses. All the hypotheses were tested at 0.05 level of significance. The results revealed that loneliness, depression and stress are significant influences of COVID-19 on the psychological wellbeing (Cal χ2 val ˃ Tab χ2 val) @ 0.05 alpha level). The study concluded that loneliness, depression and stress are influences of COVID-19 on the psychological wellbeing of the students. Therefore, it was recommended that more social programmes should be organized on television as long as lockdown is active to help students out of loneliness to support the mental health and well-being of students to save them for depression.</p> <p><strong>Keywords</strong>: COVID-19; psychological wellbeing; depression; loneliness; stress; tertiary</p> Seun Akorede Ayodotun Ajayi Atanda Toyin Gilbert Uwadia Copyright (c) 2021 2021-02-14 2021-02-14 47 1 70 79 10.4314/tjs.v47i1. Floristic Studies on Herbaceous and Grass Species Growing in the University of Lagos, Nigeria https://www.ajol.info/index.php/tjs/article/view/203425 <p>Rapid loss in flora diversity, changing patterns of vegetation and land use patterns in the University of Lagos Akoka campus has necessitated investigation on the herb and grass species so as to determine their compositions, structures and diversity within the area. Twenty sampling plots of 10m x 10m each were studied in five selected locations using random sampling. The samples were counted and identified using Flora of West Tropical Africa. A total of 75 taxa (herbs = 53 spp and grasses = 22 spp) belonging to 26 families and 64 genera were recorded in the area. Of all the families, Asteraceae and Euphorbiaceae had the highest number of species with seven species of herbaceous plants each. The Simpson index value was highest in locations A and D (0.98), Shannon index value was highest in location A (3.96); while evenness value was highest in location E (0.92). Among the herbs, <em>Asystasia gangetica</em> had the highest importance index value (40.22%), while <em>Panicum maximum</em> had the highest importance value (34.87%) among the grasses. The results revealed restricted distribution of the species in specific areas probably due to development of infrastructural facilities in the study area. It is recommended that the species with low importance values should be given priorities in terms of conservation policies for future purposes by planting them and protecting their habitats.</p> <p><strong>Keywords</strong>: Conservation; Species composition; UNILAG flora; Urbanization;</p> George Nodza Ruth Anthony Temitope Onuminya Oluwatoyin Ogundipe Copyright (c) 2021 2021-02-14 2021-02-14 47 1 80 90 10.4314/tjs.v47i1. Determination of Aquifer Parameters from Resistivity Data: A Case of University of Ilorin Campus, Northcentral Nigeria https://www.ajol.info/index.php/tjs/article/view/203428 <p>A total of twenty-one (21) vertical electrical sounding (VES) data were acquired using Pz-02 resistivity meter within the Precambrian basement area of part of Ilorin Metropolis north central Nigeria to evaluate the hydraulic characteristics of aquifers. The Schlumberger configuration with half-current electrode separation (AB/2) varying from 1 m to 60 m was used. The aquifer hydraulic characteristics such as hydraulic conductivity K and transmissivity T (Ωm2) were calculated from the interpreted VES data using the concept of Dar-Zarrouk parameters. The data, processed with computer software IPI2WIN, indicated three to four geo-electric layers, namely; topsoil, clayey (wet to dry), weathered or fractured basement and fresh basement with resistivity values ranging from 130 to 1469 Ωm, 52.6 to 8552 Ωm, 46.2 to 249 Ωm and 454 to 5022 Ωm, respectively. The depth to aquifer ranges between 6.17 m and 24.9 m and the overburden thickness ranges between 4.1 m and 22.7 m. The assessment of the materials above the aquifers showed that longitudinal conductance lies between 0.02 and 0.468 Ω–1, transmissivity values vary from 246 to 2419.8 Ωm2. The results obtained have offered worthwhile hydrologic information that will aid both exploration and exploitation of the groundwater system of the study area.</p> <p><strong>Keywords</strong>: Dar-Zarrouk parameters; aquifer; groundwater; VES; geoelectric layer</p> Babatunde Onawola Saminu Olatunji Oluwatoyin Ologe Razak Jimoh Copyright (c) 2021 2021-02-14 2021-02-14 47 1 91 103 10.4314/tjs.v47i1. Antibacterial Activities of Hyphaene thebaica (Doum Palm) Fruit Extracts against Intestinal Microflora and Potential Constipation Associated Pathogens in Yola Metropolis, Nigeria https://www.ajol.info/index.php/tjs/article/view/203431 <p>This study aimed at determining the antibacterial activities of <em>Hyphaene thebaica</em> fruit extracts against some intestinal constipation associated bacteria. Qualitative analysis of some phytochemical constituents, agar well diffusion and broth dilution methods were used to determine the zones of inhibition and minimum inhibitory concentration (MIC) of the plant extracts. Phytochemical components viz flavonoids, saponins, terpenoids, tannins, phenols, alkaloids, glycosides and steroids were detected in the plant extracts, and the test organisms were susceptible to the plant extracts. The diameter zone of inhibition (DZI) obtained with n-hexane extract ranged from 15.10 ± 0.51 mm to 2.0 ± 0.55 mm against <em>K. pneumoniae</em>, 10.20 ± 0.57 mm to 2.00 ± 0.35 mm against <em>P. aeruginosa</em> and 8.00 ± 0.35 mm to 1.00 ± 0.55 mm against <em>S. typhi</em>, while the DZI for aqueous extract was 7.10 ± 0.23 mm to 2.0 ± 0.35 mm against <em>K. pneumoniae</em>, 6.20 ± 0.31 mm to 2.00 ± 0.35 mm against <em>S. typhi</em> and 5.42 ± 0.55 mm to 2.05 ± 0.75 mm against <em>P. aeruginosa.</em> The MIC and minimum bactericidal concentration of the extracts were 100 mg/mL and 200 mg/mL, respectively. <em>Hyphaene thebaica</em> fruit possessed antimicrobial activities against the test organisms. Therefore, toxicity and clinical studies are recommended for possible drug development.</p> <p><strong>Keywords</strong>: Doum; Constipation; Intestinal; Microflora; Fibre; <em>Hyphaene thebaica.</em></p> Joel Ewansiha Chidimma Ugo Damaris Kolawole Lilian Orji Copyright (c) 2021 2021-02-14 2021-02-14 47 1 104 111 10.4314/tjs.v47i1. Corrosion Inhibition of Mild Steel in Seawater by 2,4,6-Triamino-3-Pentadecylphenyl Acetate Derived from Cashew Nut Shell Liquid https://www.ajol.info/index.php/tjs/article/view/203433 <p>The corrosion inhibition performance of 2,4,6-triamino-3-pentadecylphenyl acetate on mild steel in seawater at stationary condition, 30 °C and pH 8 was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy. The maximum inhibition efficiency of 93% was found in the presence of 300 ppm of 2,4,6-triamino-3-pentadecylphenyl acetate for both potentiodynamic polarization and electrochemical impedance spectroscopy techniques. The potentiodynamic polarization curves show that 2,4,6-triamino-3-pentadecylphenyl acetate acts as a mixed type inhibitor which influences more the anodic processes. The Nyquist plots revealed that the polarization resistance (Rp) increases whereas the double-layer capacitance (Cdl) and corrosion current density (icorr) decrease as the concentrations of the inhibitors increase due to the formation of a protective layer of inhibitor over the mild steel surface. The results obtained from the two electrochemical techniques are in good agreement. The adsorption of 2,4,6-triamino-3-pentadecylphenyl acetate on the mild steel surface obeyed Langmuir adsorption isotherm.</p> <p><strong>Keywords</strong>: Cashew nut shell liquid; 2,4,6-triamino-3-pentadecylphenyl acetate; corrosion inhibitor; mild steel; seawater.</p> Emanuel Ricky Esther Lugwisha Joseph Philip Copyright (c) 2021 2021-02-14 2021-02-14 47 1 112 122 10.4314/tjs.v47i1. Forest Structure and Climate Change Mitigation Potential: A Case of Wilolesi and Ikonongo Forested Hills in Iringa Municipality, Tanzania https://www.ajol.info/index.php/tjs/article/view/203434 <p>Vegetation plays major roles in carbon storage and ecosystem functioning by modifying the rate of carbon fluxes thereby mitigating climate change. However, the focus of assessing the potentials for different vegetation on climate change mitigation has for so long been conducted outside cities, towns and municipalities. This study was conducted in Wilolesi and Ikonongo hills located in Iringa as representative of the Municipality forested hills in Tanzania to assess vegetation structure and their potential for climate change mitigation. Random sampling technique was employed to establish 20 rectangular plots of 20 m x 40 m (0.08 ha) in each hill to determine plant species composition, richness, diversity, vegetation structure and above ground carbon (AGC). R-statistical software was used to compute Shannon-Wiener diversity indices, species richness and the above ground carbon. Results indicated high species diversity ranging from 3.5 to 4.1 for Ikonongo and Willolesi hills, respectively based on Shannon-Wiener diversity index (H’). We recorded 255 plant species (114 tree species, 51 shrub species, 2 sedge species, 66 herb species, 15 grass species and 7 climbers) in 60 families. Based on Important Value Index (IVI), <em>Brachystegia spiciformis</em> Benth (10.435) and <em>Julbernardia globiflora</em> Benth (4.555) were important species in Wilolesi and Ikonongo forested hills. There was a significant difference on the AGC between Ikonongo (3.12 t/ha) and Wilolesi (8.33 t/ha) (t = 1.83, p = &lt; 0.004). Results have an implication for dedicating more efforts on the management of forest landscapes for biodiversity conservation, climate change mitigation and provision of other ecosystem services. It is recommended that there should be detailed study for all forested hills in Iringa Municipality for proper forest management initiatives.</p> <p><strong>Keywords</strong>: Climate change mitigation potential; forest structure; forested hills</p> Evarist Fundisha Hamidu Seki Anasia Saria Copyright (c) 2021 2021-02-14 2021-02-14 47 1 123 133 10.4314/tjs.v47i1. Seismic Attributes Analysis as a Precursor to Hydrocarbon Indicators: A Case Study of “Ok” Field, Niger Delta https://www.ajol.info/index.php/tjs/article/view/203570 <p>Seismic data volume was employed to gain more insights into the complexities of the hydrocarbon hosting units within and outside the vicinity of well control in the OK-field Niger Delta to overcome wrong deductions from complexly faulted subsurface configuration for the oilfield exploration programme. The methodology involved integration of well log with seismic data, seismic structural analysis and seismic attributes analysis. Horizons and fault interpretations were carried out to produce subsurface attribute maps. Lithologic panels derived from well log data showed that the study area is characterized by sand-shale interbedding. Two hydrocarbon bearing reservoirs were delineated within the study interval, namely: R1 and R2. Well to seismic tie revealed that these horizons tied direct hydrocarbon indicators (bright spots) on the vertical sections. Structural interpretation revealed that “OK” field is characterized by a rollover anticline, with a closed trapping mechanism for the D series and fault/dip trapping mechanism in the E series. The conclusion of the study was that the highly prospective areas are where bright spots were observed, while areas with dim spots are less prospective. The study has shown the ability of instantaneous amplitude as a requisite in prospect identification and reservoir prediction.</p> <p><strong>Keywords</strong>: reservoirs; fault; hydrocarbon; seismic; amplitudes; structures;</p> Oluwatoyin Ologe Mary Olowokere Copyright (c) 2021 2021-02-14 2021-02-14 47 1 134 144 10.4314/tjs.v47i1. HIV/AIDS Transmission Dynamics: Modelling the Roles of Long Distance Truck Drivers https://www.ajol.info/index.php/tjs/article/view/203571 <p>A mathematical model to investigate the roles of long distance truck drivers on HIV transmission dynamics was formulated and analyzed to establish the existence of disease free and endemic equilibrium points. The results show that, the disease free equilibrium point is asymptotically stable when the basic reproduction number is less than unity and unstable otherwise. Furthermore, comprehensive analyses on the two steady states (infection free and endemic) have shown that they are both globally and asymptotically stable. Sensitivity analysis is performed on the reproduction number in order to establish the relative importance of parameters, and it shows that the truck drivers have the potential of increasing the rates of transmission of HIV infections, which concurs with the numerical simulation results.</p> <p><strong>Keywords</strong>: Truck drivers; stability; equilibrium; reproduction number; sensitivity.</p> Nyimvua Mbare Copyright (c) 2021 2021-02-14 2021-02-14 47 1 145 162 10.4314/tjs.v47i1. Mobile Pedestrian Navigation Framework for Multi-factors Resources Allocation https://www.ajol.info/index.php/tjs/article/view/203572 <p>Abstract<br>Although it is possible for pedestrian to walk to unfamiliar places, familiarizing and finding a way out of new environments is quite challenging unless a pedestrian navigation system (PNS) is used. Most existing PNS solutions are employing vehicle navigation framework, however, such systems are designed to work efficiently for vehicular systems and not suitable for finding shortest path in environment with poor geospatial mapping. This study designed pedestrian navigation framework for PNS that supports resource allocations in environment with poor geospatial mapping. Mixtures of qualitative and quantitative methods have been used to interview prospective users for requirement specifications and experimental research for designing the framework, respectively. Prototyped route network framework with routing data were implemented using Open source QGIS software, and a route analysis achieved using QGIS shortest path network analysis. The resulted framework shows more than 3.5% improvement between optimal routes established by PNS on proposed framework as compared to optimal route established by existing systems.</p> <p><strong>Keywords</strong>: Mobile; Pedestrian; Navigation; System; Framework</p> Joseph Mushi Baraka Jungwa Copyright (c) 2021 2021-02-14 2021-02-14 47 1 163 179 10.4314/tjs.v47i1. Analyzing the Electricity Consumption and Costs of Electrical-Powered Machines When There is Orepass Failure in Underground Mine https://www.ajol.info/index.php/tjs/article/view/203575 <p>Abstract<br>In underground mining environment where the loss of orepasses is a dominant factor, the mine may face a challenge of improving the loading and hauling operations. Some of the options will be to rehabilitate the lost orepasses, or developing the new ones. When the rehabilitation cost is high, alternative strategies should be applied to compensate for the orepasses failure. One of the possible options is to use diesel or electric Load-Haul-Dumps (LHDs). The use of diesel-powered LHDs will increase heat and gas emissions which increase environmental concerns and ventilation costs, while adoption of electric-powered vehicles needs to be analysed. Therefore, this study was conducted at an existing underground mine in Sweden, to determine the electricity consumption and costs of electric-powered LHDs when there is a loss of orepasses. The AutoModTM discrete event simulation tool was used during the analysis. The results show that, electric-powered LHDs have significant cost saving when used in case of orepass loss to move materials compared to diesel-powered units. However, the source of electricity to fully adopt electric-powered units may need further financial justifications to evaluate the impacts to the environment.</p> <p><strong>Keywords</strong>: Electricity costs; production rate; discrete event simulation; loading operations.</p> Bartłomiej Skawina Abubakary Salama Copyright (c) 2021 2021-02-14 2021-02-14 47 1 180 193 10.4314/tjs.v47i1. Application of Guided Local Search (GLS) in Portfolio Optimization https://www.ajol.info/index.php/tjs/article/view/203617 <p>Portfolio optimization is a major activity in any operating business. Conventional portfolio optimization research makes simplifying assumptions; for example, they assume no constraint in how many assets one holds (cardinality constraint). They also assume no minimum and maximum holding sizes (holding size constraint). Once these assumptions are relaxed, conventional methods become inapplicable, and hence new methods are needed to tackle this challenge. Threshold Accepting is an established algorithm in the extended portfolio optimization problem. In this paper, an algorithm called Guided Local Search (GLS) is applied using an accurate and efficient designed hill climbing algorithm, named HC-C-R. GLS sitting on HC-C-R is for the purpose of solving the extended portfolio optimization problem. The improved hill climbing algorithm is tested on standard portfolio optimization problem. Results are compared (benchmarked) with the Threshold Accepting (TA) algorithm, a well-known algorithm for portfolio optimization and are also compared with its original algorithm HC-C-R. Results show that GLS sitting on HC-C-R is more effective than HC-C-R and the algorithms are more effective than TA.</p> <p><br><strong>Keywords</strong>: Portfolio Optimization; Algorithm; Guided Local Search; GLS, Threshold Acceptance</p> Collether John Copyright (c) 2021 2021-02-14 2021-02-14 47 1 194 203 10.4314/tjs.v47i1. Cellulase-Producing Bacteria Isolated from Mufindi Paper Mill Industrial Effluent, Iringa Tanzania https://www.ajol.info/index.php/tjs/article/view/203577 <p>Effluent and effluent-contaminated soil samples collected from Mufindi Paper Mill Limited, Iringa Tanzania were investigated for the presence of cellulolytic bacteria. The components of cellulase are endoglucanase, exoglucanase and β-glucosidase and these are very important for complete hydrolysis of cellulose to glucose monomers. Isolates were grown on nutrient agar and screened for cellulolytic activity on carboxymethylcellulose (CMC) agar plates using Gram’s iodine solution. Cellulases activities; endoglucanase, exoglucanase and β-glucosidase were assayed using CMC, avicel and cellobiose substrates, respectively by dinitrosalicyclic acid method. Out of 17 cellulolytic isolates obtained, crude enzyme extracts of only five isolates expressed all cellulases activities, the highest activity being on cellobiose followed by CMC and least on avicel. The maximum endoglucanase (0.0701 ± 0.010 U/ml), exoglucanase (0.0081 ± 0.001 U/ml) and β-glucosidase (0.0738 ± 0.002 U/ml) activities from submerged fermentation culture were observed from isolate 8, 1 and 12, respectively. Based on 16S rRNA sequences analyses, three isolates were identified as <em>Pararheinheimera mesophila</em>, <em>Bacillus cereus</em> and <em>Bacillus flexus</em>. The other two isolates were identified as <em>Bacillus megaterium</em>.</p> <p><strong>Keywords</strong>: Cellulose; Endoglucanase; Exoglucanase; β-glucosidase; 16S rRNA</p> Erick Sinza Aneth Mwakilili Cyprian Mpinda Sylvester Lyantagaye Copyright (c) 2021 2021-02-14 2021-02-14 47 1 204 213 10.4314/tjs.v47i1. Capacity Analysis of a Television White Space Network Deployed under Distance Distribution Approach https://www.ajol.info/index.php/tjs/article/view/203579 <p>Television White Space (TVWS) is currently a leading technology for broadband connectivity in rural areas due to its penetration capability and robustness to attenuation and fading. Since most rural areas where TVWS is suitable are characterized by sparse population distribution, a deployed network must be adequately planned to provide the required coverage while meeting the targeted quality of service. This paper modelled and analyzed the capacity of a TVWS suitable for sparsely populated settings. The TVWS network was modelled using the distance distribution approach, and capacity simulation was carried out through Matlab. Results showed that, at the signal quality of just 10 dB, a network of one BS and 10 CPEs (Customer Premise Equipment), achieved a channel capacity of 18 Mbps and user downlink capacity of 2 Mbps. These results are better than the trials conducted in a similar environment in the sub-Saharan Africa region.</p> <p><strong>Keywords</strong>: TVWS; CPE; SINR; Rural Broadband; PPP</p> Moses Ismail Mussa Kissaka Prosper Mafole Copyright (c) 2021 2021-02-14 2021-02-14 47 1 214 227 10.4314/tjs.v47i1. Multi-Bands Circular Ring Monopole Antenna with Double L-Shape for WLAN/WiMAX Applications https://www.ajol.info/index.php/tjs/article/view/203581 <p>The rapid growth of technology increases the demands of low profile and compact antennas, supporting different wireless systems standards in mobile devices. Recently, several multi-band antenna designs have been proposed for mobile devices due to the current advancement of antenna technology. In this paper, a multi-band circular ring with a double L-shaped monopole antenna for Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) applications is presented. The proposed antenna consists of a circular-shaped and rectangular strip connected with two inverted L-shaped trips. The H-shaped-strips are attached within the rectangular-strips. The antenna is fed by a 50 Ω micro-strip line, and it operates at three resonant frequencies, which include 2.4 GHz and 3.5/5.5 GHz for WLAN and WiMAX applications, respectively. The antenna has been simulated using CST Microwave Studio software. The proposed antenna achieved impedance bandwidth of 284 MHz, 368 MHz, and 1120 MHz for 2.4 GHz, 3.5 GHz, and 5.5 GHz frequency bands, respectively, while the corresponding antenna gains are 1.28 dB, 1.78 dB, and 2.78 dB. The antenna has a compact dimension size of 18 x 28 x 1.6 mm3 when printed on the FR-4 substrate of dielectric constant 4.3.</p> <p><strong>Keywords</strong>: monopole antenna; multi-band antenna; WLAN; WiMAX and inverted L-shaped strips</p> Hassan Mkindu Hashim Iddi Copyright (c) 2021 2021-02-14 2021-02-14 47 1 228 242 10.4314/tjs.v47i1. Monthly and Seasonal Rainfall Concentrations and Predictability in Tanzania https://www.ajol.info/index.php/tjs/article/view/203612 <p>This study aimed at determining the monthly and seasonal rainfall concentration, predictability and the changes in rainfall seasons in Tanzania. Rainfall predictability was determined using Colwell’s indices, Rainfall Concentration Index (RCI) and Coefficient of Variation (CV). Results showed that rainfall in December–February (DJF), January–March (JFM) and February–April (FMA) has predictability due to constancy of 60%, RCI ≤ 9 and CV &lt; 0.4 in Lake zone, Central zone, Southern Coast zone, Western and Southern Highlands zone. Rainfall in October to December (OND) was reliable in the Island zone, North-Eastern highlands zone and Northern coast zone with an average predictability due to constancy of 65%. In the Lake zone, all seasons (DJF, JFM, FMA, MAM, OND and DJFMAM) had uniform rainfall distribution (RCI = 8.7, CV = 0.35) and predictability due to constancy of 80% which leads to the conclusion that Lake Zone has unimodal rainfall distribution. Rainfall predictability in Tanzania has a West-East gradient. The western zones had an average predictability due to constancy of 68%. In general, rainfall in Tanzania is observed to be highly variable; only 20% of the predictability is concerned with reliability in the rainfall occurrence within the seasons and 80% is due to seasonality.</p> <p><strong>Keywords</strong>: Rainfall concentration index; predictability; coefficient of variation; seasonality; constancy</p> Pasvolo Mwinuka Christian Uiso Ladslaus Chang’a Mwingereza Kumwenda Copyright (c) 2021 2021-02-14 2021-02-14 47 1 243 257 10.4314/tjs.v47i1. Effects of Drying, Packaging Conditions and Storage Time on Proximate Composition of Chia Seeds (Salvia hispanica) https://www.ajol.info/index.php/tjs/article/view/203613 <p>The effects of drying, packaging conditions and storage time on proximate composition of chia seeds were investigated. Chia seeds were dried at 63 °C for 30 min (low-temperature long time–LTLT) and at 75 °C for 30 s (high-temperature short time-HTST) using dry oven, air/vacuum-packed and stored for ten weeks. The effect of heat processing (drying) on chia seeds had significant difference (p &lt; 0.05) in ash, fiber and fat contents while there was no significant difference (p &gt; 0.05) in moisture and protein contents. Except for fiber content, there was no significant difference (p &gt; 0.05) in moisture, ash, fat and protein of chia seeds dried at LTLT and HTST before storage. During storage time, there was significant decrease of proximate composition of chia seeds and the decline was the lowest in raw chia seeds followed by seeds dried at HTST and the highest by seeds dried at LTLT. In both drying conditions, ash, fat and protein contents were significantly greater in vacuum than in air packaging although the impact was vice versa for moisture and fiber contents. On the expense of improved shelf life, palatability and digestibility expected as effect of drying, this study suggests HTST and vacuum packaging for storage of chia seeds.</p> <p><strong>Keywords</strong>: Chia seeds; proximate composition; drying; packaging condition; storage.</p> Ashura Katunzi-Kilewela Leonard Rweyemamu Oscar Kibazohi Lilian Kaale Copyright (c) 2021 2021-02-14 2021-02-14 47 1 258 267 10.4314/tjs.v47i1. A Model for Mapping Combined Effects of Quality of Service Parameters and Device Features on Video Streaming Quality of Experience https://www.ajol.info/index.php/tjs/article/view/203614 <p>Maintaining quality of streaming video is challenged by network faults resulting into freezes and rebufferings on the video. On top of the network effects, device features have impacts on the image of the video frames displayed during streaming. Despite the simultaneous impacts of video quality from network and device, previous studies considered individual impact of network parameters or devices as influencing factors to propose Quality of Experience (QoE) models. This study proposed QoE model by mapping combined effects from both network and device on video streamed QoE. An experiment to study the effects of video quality from combined effects of network and device over the wireless involved 35 subjects. Combination of packet loss, packet reordering, and delay were emulated using network emulator following Design of Experiment methodology. Through analysis of variance, the study found that packet loss had the highest impact, followed by device features, reordering, and delay on the video QoE. From the combined effects, two-way interactions and three-way interactions had significant effects on the video QoE. Through additive and linearity behavior of the input factors from network and device on video streaming QoE, a multi-factor model was derived.</p> <p><br><strong>Keywords</strong>: Design of Experiment (DOE); Mean Opinion Score (MOS); Quality of Experience (QoE); Quality of Service (QoS); Video Quality Assessment</p> Beatrice Buberwa Mercy Mbise Copyright (c) 2021 2021-02-14 2021-02-14 47 1 268 281 10.4314/tjs.v47i1. Effects of Plant Species Diversity and Biomass on Grazing Patch Selection by Semi Free-Ranging Cattle https://www.ajol.info/index.php/tjs/article/view/203615 <p>Studies examining forage selection by large herbivores have generally focused on single herbivore-plant relationships and few studies link plant species diversity with large herbivore feeding preferences, particularly in species-rich ecosystems. A study was therefore conducted to examine how herbaceous plant biomass, species richness, diversity and evenness, together with elevation and distances to houses, agricultural fields and cattle holding-pen areas (kraals), predict cattle grazing intensity at small (0.5 x 0.5 m) and large (20 x 50 m) patches by semi free-ranging indigenous cattle in Kilombero Valley Floodplain wetland Tanzania. Results showed that cattle grazed patches with high species richness and intermediate level of biomass at a small spatial scale, suggesting that selection of small patches is a trade-off between food quality and quantity. On a larger scale, cattle grazed patches with a higher abundance of palatable plant species with high biomass, but with less plant species diversity. Moreover, grazing intensity in large patches was positively related to elevation and distance from agricultural fields. Overall, this study shows that considering both plant community properties and physiographic variables in forage selection studies facilitates a better understanding of grazing ecology of large domestic herbivores in species-rich ecosystems. Thus, maintenance of plant species richness and biomass in wetland rangelands is important to improve domestic herbivore production and conservation of biodiversity.<br><strong>Keywords</strong>: Domestic herbivore; Forage selection; plant-animal interaction; Rangelands; Species richness</p> Samora Andrew Copyright (c) 2021 2021-02-14 2021-02-14 47 1 282 295 10.4314/tjs.v47i1. Acetylcholinesterase Activity and Oxidative Stress Biomarkers in Fiddler Crabs (Austruca occidentalis) along the Coastal Mangrove Areas of Dar es Salaam, Tanzania https://www.ajol.info/index.php/tjs/article/view/203616 <p>The aquatic organisms such as crustaceans serve as bioindicators of the environmental stressors which affect the aquatic ecosystems. The present study assessed environmental health status through fiddler crabs (<em>Austruca occidentalis</em>) towards oxidative stress biomarkers and AChE activity in mangroves with different levels of salinity and environmental contamination. Fiddler crabs were collected from Mtoni Kijichi, Kunduchi and Mbweni, which experience different levels of contamination from high to low along the Dar es Salaam coastline. Malondialdehyde the biomarker of oxidative stress was analysed by lipid peroxidation (LPO) assay and AChE activity was tested using Ellman assay in the crab tissues (muscles, hepatopancreas and gills). To this end, the results showed a significant variation in the LPO levels in analysed tissues (p &lt; 0.05) with relatively higher level observed in hepatopancreas, 1.799 μM MDA/mg w.wt than in muscles and gills 0.924 and 1.378 μM MDA/mg w.wt, respectively. Although there was variation of LPO levels in <em>A. occidentalis</em> among the studied sites as well as between salinity levels, the variation was not statistically significant (p &gt; 0.05). The AChE activities in <em>A. occidentalis</em> were significantly different among the study sites (p &lt; 0.05), with Mbweni having lowest (4.791 nmol/min/mg protein) activity followed by Kunduchi (4.965 nmol/min/mg protein) and lastly Mtoni Kijichi (5.321 nmol/min/mg protein). The AChE activity also varied significantly by tissue (p &lt; 0.05), whereas hepatopancreas and gills had lowest enzyme activity (4.254 and 4.534 nmol/min/mg protein, respectively) as compared to muscles (6.290 nmol/min/mg protein). This field study provides information on the usefulness of <em>A. occidentalis</em> in assessing the health status of marine costal ecosystems through their responses against toxicants.</p> <p><strong>Keywords</strong>: Fiddler crabsn; Oxidative stress; Bioindicators; Acetylcholinesterase</p> James Lugata Flora Stephano Harishchandra Pratap Copyright (c) 2021 2021-02-14 2021-02-14 47 1 296 307 10.4314/tjs.v47i1. Modelling Road Traffic Accidents Counts in Tanzania: A Poisson Regression Approach https://www.ajol.info/index.php/tjs/article/view/203895 <p>Road traffic accidents have become serious threats to Tanzanians in recent years. The outcry<br>emanates from the increasing prevalence of negative effects of accidents on human lives,<br>properties, environments and the economy. Poisson regression model was used to study the<br>relationship between road accidents and the factors facilitating them in Tanzania. Count data on<br>yearly road traffic accidents for Tanzania covering the period 1993 to 2019 were used. Due to<br>over-dispersion of Poisson regression model, quasi-Poisson regression model was found the most<br>appropriate approach for the analysis of these data. Results indicated that all predictors are<br>significant under Poisson regression model with p-value less than 0.05 but high speed was found<br>insignificant using quasi-Poisson regression model. All factors causing road accidents predicted<br>minor increase of accidents, showing that current control measures on road accidents are likely to<br>be effective.<br><strong>Keywords</strong>: Road accidents; Poisson regression, Over-dispersion; Deviance, Variance inflation<br>factor.</p> Thadei Sagamiko Nyimvua Mbare Copyright (c) 2021 2021-02-14 2021-02-14 47 1 308 314 10.4314/tjs.v47i1. Campylobacteriosis Transmission Dynamics in Humans: Modeling the Effects of Public Health Education, Treatment, and Sanitation https://www.ajol.info/index.php/tjs/article/view/203898 <p>Abstract<br>An epidemic model for the dynamics of campylobacteriosis disease with public health education, treatment, and sanitation control strategies was formulated and analyzed. The stabilities of the equilibrium points were analyzed by using the Routh-Hurwitz criterion. The effective reproduction number was computed by using the Next Generation Matrix method. Numerical simulations were carried out and the results showed that, public health education has a substantial influence on the reduction of the effective reproduction number. Moreover, treatment and sanitation control strategies have also shown significant reduction of infected individuals from the respective population.</p> <p><br><strong>Keywords</strong>: Campylobacteriosis; public health education; treatment; sanitation</p> Furaha Chuma Zubeda Mussa Copyright (c) 2021 2021-02-14 2021-02-14 47 1 315 331 Physicochemical and Sensory Evaluation of Mixed Juices from Banana, Pineapple and Passion Fruits during Storage https://www.ajol.info/index.php/tjs/article/view/203899 <p>Juices from fresh fruits offer various health benefits, including strengthening the immune system and preventing diseases. Mixed fruit juices tend to have good nutritional contents and organoleptic properties like colour, flavour, taste, and overall appeal of different fruits. This work investigated the physicochemical and sensory attributes of fruit juice of low viscosity banana juice blended with pineapple and passion juices. The prepared juices were pasteurised at 92 °C for 15 s, bottled in air-tight glass bottles, and subsequently stored in two different conditions: an ambient temperature of approximately 28 ± 2 °C and a fridge at 4 ºC for one month. Ascorbic acid content, total soluble solids, acidity, pH, and sensory evaluation were measured during the storage period. The results revealed that ascorbic acid and pH decrease significantly (p &lt; 0.05) as the acidity increases. The changes ranged between 16 and 37% for ascorbic acid, 0.8 and 1.8% for pH, and from 12 to 27% for acidity were observed. The total soluble solids were found to increase until ten days of storage. The control samples showed no changes in all the physicochemical properties analysed during storage. The juice sample that consisted of 80% banana juice and 20% passion juice emerged as the utmost imperative sample as it scored the highest hedonic scale on all sensory attributes. The results imply that low viscosity banana juice can be used as a major component for the preparation of commercial mixed juices.</p> <p><strong>Keywords</strong>: Banana Juice; Chemical Analysis; Sensory Evaluation; Mixed Juice</p> Victor Matabura Oscar Kibazohi Copyright (c) 2021 2021-02-14 2021-02-14 47 1 332 343 Effects of Time on pH, Total Bacteria Counts, and Total Hydrocarbon Contents in the Bioremediation of Crude Oil Contaminated Soil Using Indigenous Bio-stimulants https://www.ajol.info/index.php/tjs/article/view/203900 <p>This study was conducted to investigate the effect of time on pH, total bacteria counts, and total hydrocarbon contents in the bioremediation of crude oil contaminated soil using pig waste and sawdust as bio-stimulants. Dried soil samples (500 g each) were weighed each into seven different plastic bowls, and each bowl was contaminated with 10 g of crude oil. Six of the contaminated soil samples in six of the plastic bowls were amended with a combination of pig waste and sawdust as bio-stimulants in the ratio of 1:1 in amounts of 150 g, 125 g, 100 g, 75 g, 50 g, and 25 g, while the seventh bowl served as control. The bio-stimulants were not added to the control sample. The effect of time on pH, total hydrocarbon contents (THC), and total bacteria counts (TBC) were monitored in all seven samples (test samples and control) for seven weeks. Results showed that changes in the pH values for the amended samples with masses 150 g, 125 g, 100 g, 75 g, 50 g, and 25 g were within the range of 6.00–7.00 (slightly acidic to neutral) which is suitable for most plants to thrive. There were relative increase and decrease in total bacteria counts with time reflecting an unsteady trend. There was also a steady decrease in THC with an increase in detention time in all samples which indicated steady decomposition of the crude oil contaminants during storage. Also, a significant level of bioremediation was achieved using the locally sourced biomaterials as amendments.</p> <p><br><strong>Keywords</strong>: Bioremediation; Biodegradation; Time; Contaminated soils; Bio-stimulant</p> Ita Uwidia Osalodion Uwidia Copyright (c) 2021 2021-02-14 2021-02-14 47 1 344 353 Analysis of a Reform Option for the Tanzanian Pension System https://www.ajol.info/index.php/tjs/article/view/203901 <p>In this study, an analysis of a reform option for the Tanzanian pension system was done. The current system is dominated by mandatory defined benefit operating under pay-as-you-go principles. The retirement benefits are based on the average of the three best final salaries in the ten years preceding retirement. Several studies and international experts have shown that such systems face unsustainability. We propose a reform to a notional defined contribution system in which the benefits depend on accumulated contributions indexed by internal rates of returns. Simulation of results for a time horizon of fifty years shows that the notional defined contribution reform will much improve the sustainability of the pension system. The liabilities are lower and allow higher funding ratios. Also benefit payouts are lower and improve cash flows.</p> <p><br><strong>Keywords</strong>: pay-as-you-go defined benefit; pension reform; defined contribution; notional defined contribution</p> Andongwisye Mwakisisile Torbjörn Larsson Copyright (c) 2021 2021-02-14 2021-02-14 47 1 354 365 Analysis of Repeated Milk Yields and Composition Traits by Mixed Models for Crossbred Holstein Friesian Dairy Cows https://www.ajol.info/index.php/tjs/article/view/203902 <p>This study evaluated the effects of milking month, milking time, and lactation stage on milk yield and composition traits of crossbred dairy cows. Twelve crossbred Holstein Friesian cows with the same parity were purposefully selected and categorized into three groups; each consisting of four. All cows were individually managed for 120 days. Milk yield record was done every day for the morning and evening time whereas milk samples were taken every fifteen-day intervals. Data collected were analysed by PROC MIXED procedure of SAS 9.4. The “morning milkings” in all milking months showed the highest variations for “milk yield” whereas the “evening milkings” showed the highest variations for “milk urea nitrogen” in the 1st and 2nd and for “fat” in the 3rd and 4th months. The main findings in this study were the month-to-month variations in milk composition and milk yield within milking times. Milk fat was the only component that was significantly influenced by milking month, milking time, and lactation stage. Finally, this study concluded that repeated measurements for the respective milking times in milk yield and milk composition at a monthly interval showed variations. Further study should be conducted using repeated measurements at a weekly level for early detection of yield and quality alterations and health disturbances of dairy cows.</p> <p><strong>Keywords</strong>: lactation stage; milk compositions; milking month; milking time; milk yield</p> Ewonetu Senbeta Kefelegn Kefenie Adane Abebe Copyright (c) 2021 2021-02-14 2021-02-14 47 1 366 377 Mineralogy and Geochemistry of Shale-Hosted Copper of the Middle Buanji Group, Chimala Area, South-Western Tanzania https://www.ajol.info/index.php/tjs/article/view/203903 <p>The mineralogical and geochemical assessments are presented in this paper to constrain the mineralogy and copper concentrations of the shale-hosted copper in the Middle Buanji Group of the Upper Paleoproterozoic (1.67 Ga). The XRD analysis revealed that illite and chamosite are the major clay minerals present in the shales together with pseudomalachite, quartz, and muscovite that constitute over 95% by proportion of the sample. The minerals biotite, birnessite, ferroselite, bearsite, chloritoid, and anatase are present in association with shale-hosted copper in low amounts (i.e., &lt;5% by proportion of the sample). The pseudomalachite [Cu5(PO4)2(OH)4] is considered as ore mineral of copper in the shales of the Middle Buanji Group. Field observations revealed the presence of different shale layers within the Middle Buanji Group such as red, grey and green/blue in which copper mineral is distributed. On average, the copper concentrations in the shale layers were unevenly distributed throughout the red-grey-green shales layers with values of 0.31 wt%, 5.2 wt% and 13.19 wt%, respectively. A noticeable amount of copper mineralization up to 25.7 wt% was restricted within the green shale layer as compared to red (0.31 wt%) and grey (10.9 wt%) layers.</p> <p><strong>Keywords</strong>: Pseudomalachite; Supergene enrichment; Shale-hosted copper; Green shale layer</p> Almachius Mutasingwa Michael Msabi Neema Jackson Seetharamaiah Jagarlamudi Copyright (c) 2021 2021-02-14 2021-02-14 47 1 378 389 Effectiveness of Common Household Washing of Tomatoes on the Removal of Pesticide Residues https://www.ajol.info/index.php/tjs/article/view/203904 <p>The effectiveness of common household washing processes of tomatoes on the removal of pesticide residues was investigated in Iringa, Tanzania. Analyses of cleaned-up extracts were carried out using gas chromatography-mass spectrometry (GC-MS). Nine pesticide residues were detected in unwashed and washed samples. The compounds detected were chlorothalonil, pirimiphos-methyl, chlorpyrifos, profenofos, endosulfan sulphate, endosulfan ether, lambda cyhalothrin, cypermethrin and metalaxyl. The concentrations of chlorothalonil, pirimiphos-methyl, chlorpyrifos, profenofos, cypermethrin and lambda cyhalothrin in some unwashed and washed samples exceeded the maximum residue limits (MRLs). Washing reduced the concentrations of chlorothalonil and endosulfan sulphate in tomatoes by 22.2–98.0% (mean = 70%) and 33.3–55.6% (mean = 44.4%), respectively. The effectiveness of washing processes on the removal of pirimiphos methyl, chlorpyrifos and profenofos residues in tomatoes had mean values of 78.1%, 73.2% and 47.4%, respectively. The mean reduction of cypermethrin residues due to washing process was 70.2%, whereas that for lambda cyhalothrin was 56.7%. The effectiveness of washing process on the removal of metalaxyl residues had a mean of 44.9%. The results have shown that household washing removes large amounts of pesticide residues from contaminated crop produce, although large proportions of some compounds remain and can pose health risks to the consumers.</p> <p><strong>Keywords</strong>: pesticide; organophosphorus; pyrethroid; organochlorine; tomato; household washing;</p> John Mahugija Flaviana Ngabala Faustin Ngassapa Copyright (c) 2021 2021-02-14 2021-02-14 47 1 390 404