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Tanzania Journal of Science
Number of Followers: 4  

  This is an Open Access Journal Open Access journal
ISSN (Print) 0856-1761
Published by African Journals Online Homepage  [261 journals]
  • Carbon Monoxide Oxidation on Model Planar Titania Supported Platinum
           Nanoparticles Catalyst

    • Authors: Jovine Emmanuel, Brian Hayden
      Pages: 235 - 244
      Abstract: A high-throughput (parallel) thermographic screening methodology was developed to enable the measurements of the particle size and support influence on heterogeneous catalysts. A high throughput screening chip has been used to establish the catalytic activity of titania supported platinum nanoparticles catalyst for CO oxidation reaction. The catalytic activity of Pt nanoparticles between 1.3 to 7.8 nm has been investigated for CO conversion at a pressure of 0.11 and 1.1 mbar with O2:CO ratio of 1:1 at 80 °C and 0.6, 1.1 and 2.4 mbar at O2:CO ratio of 1:1 at 240 °C. At these experimental conditions, there was an increase in the TOF with decreasing particle size for instance, at 80 °C and O2:CO ratio of 1:1, total pressure of 0.11 and 1.1 mbar, the TOF increased from 0.01 s–1 to 0.171 s–1 with decreasing Pt particle size from 7.8 to 1.3 nm, respectively. However, Pt nanoparticles catalyst displayed higher activity at higher temperature, for example, the TOF increased from 3.312 s–1 to 4.355 s–1 at O2:CO ratio of 1:1, total pressure of 0.6 and 1.1 mbar, respectively, for Pt particle size of 1.3 nm in agreement with the previous reports. Results show that CO oxidation on titania supported Pt nanoparticles catalyst is particle size dependent. On the other hand, findings from XPS measurements show no major change in the particle size after the reaction thus, reflecting the stability of Pt particles. While there is no apparent consensus in the literature reports on the activity trend with particle size for this system, these findings are consistent with most of the previously reported findings. Keywords: platinum; titania; nanoparticles; thermography; CO oxidation.
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.1
      Issue No: Vol. 48, No. 2 (2022)
       
  • Impact of Radio Operating Environments on Broadband Connectivity

    • Authors: Libe V Massawe, Peter J Chitamu
      Pages: 245 - 255
      Abstract: Broadband connectivity and services commonly referred to as the Internet is the key enabling facility for the modern digital economy and the driver for the Fourth Industrial Revolution (4IR or Industry 4.0). In Tanzania, there are over 49% Internet subscriptions for mobile broadband services using 3G UMTS and 4G standards infrastructure, which are predominantly available in urban areas. The non-urban areas remain mostly 2G coverage areas and lack mobile broadband connectivity and services. Transforming existing 2G mobile networks to broadband infrastructure can be achieved by swapping 2G sites with 3G or 4G sites or incrementally replacing 2G sites with 3G or 4G sites on demand. In this work, we investigated the performance of the UMTS family of standards to deliver broadband connectivity and services outside major towns and cities in three different radio operating environments, namely hilly, undulating and flat terrain landscapes. Results show that the achievable 3G data rate deteriorates depending on the type of operating environment as the internet user moves away from the base station. Therefore, mobile broadband deployment in non-urban areas is not simply replacement of 2G sites for 3G sites; it will require special deployment strategies to achieve a total broadband coverage. Keywords: Internet Services; Mobile Broadband; Radio Channel Modelling; Telecoms Industry Innovation; Sustainable Infrastructure Development
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.2
      Issue No: Vol. 48, No. 2 (2022)
       
  • Effects of Biochar on Soil Fertility and Crop Yields: Experience from the
           Southern Highlands of Tanzania

    • Authors: Peter M. Rogers, Pius Z. Yanda, Noah M. Pauline, Simon Haikola, Anders Hansson , Mathias Fridahl
      Pages: 256 - 267
      Abstract: The world’s agricultural production is declining due to severe loss of soil fertility through natural processes or because of human activities. Biochar has been identified as a potential soil amendment to regain its fertility and increase crop productivity. This study aimed to assess the effects of biochar on soil nutrients and crop yields in the southern highlands of Tanzania. Data were collected through key informant and household interviews, and from sampling of soils in coffee farms where biochar of maize cobs origin was incorporated at the rate of 3 t ha-1. Purposive sampling approach was deployed to identify the villages in which farmers have been incorporating biochar in farms. A total of 172 households, 30 key informants, and 12 top and subsoil samples were involved in this study. Quantitative data were analyzed using SPSS version 20, and excel spreadsheet was used for descriptive results and relationships. The findings revealed that biochar significantly increased soil pH, iron (Fe), organic carbon (OC), cation exchange capacity (CEC) and exchangeable bases (potassium-K, magnesium-Mg). T - tests showed significant increase of soil nutrients in biochar treated soils. In addition, biochar increased coffee and maize yields from 1 t ha-1 to 3 t ha-1. Keywords: Biochar; Soil Nutrients; Food Security; Resilience; Adaptation
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.3
      Issue No: Vol. 48, No. 2 (2022)
       
  • Seasonality in Phytoplankton Species Composition and their Influence on
           Small Pelagic Fish along the Western Pemba Channel

    • Authors: Margareth S Kyewalyanga
      Pages: 268 - 282
      Abstract: The influence of phytoplankton biomass on small pelagic fish groups was studied at three sites along the Western Pemba Channel, to assess the contribution of seasonality. Sampling took place at the three sites in the coastal waters of Tanga, Tanzania. The study used in-situ data from July 2016 to January 2017, remotely-sensed chlorophyll-a data from August 2016 to August 2017 and 2019–2020, and small pelagic fish catch data from the same periods as the remotely-sensed data. The dominant groups at all the three sites were diatoms, dinoflagellates, and cyanobacteria, with diatoms having the highest number of species compared to the other two. In comparison to the southeast monsoon season, phytoplankton species and biomass were significantly higher during the northeast monsoon season. The most plentiful fish were anchovies, which had high peaks in both seasons, followed by sardinella, while mackerel had the lowest catch. Chlorophyll-a and anchovy catches showed a positive correlation; however, the relationship was not significant (r = 0.47, df = 11, p = 0.12). Both variables showed the highest peaks in October, while other fish groups showed very weak and insignificant positive or negative correlations. These findings suggest that factors other than phytoplankton biomass contribute to controlling small pelagic fish availability. Keywords: Phytoplankton; monsoon seasons; chlorophyll-a; Pemba Channel; small pelagic fish.
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.4
      Issue No: Vol. 48, No. 2 (2022)
       
  • Characterization of Clay and Granite Dust Blends as Novel Materials for
           Energy Storage and Diffuser in Constructing Flat-plate Solar Collector

    • Authors: Tajudeen Kolawole Ajiboye, Mustapha Olawale Fabiyi, Ndagi Mustapha , Sulaiman Abdulkareem
      Pages: 283 - 293
      Abstract: Sun is the main source of solar energy, and the energy it releases to the Earth’s surface in one hour is more than what the whole planet consumes in a year. This present work is about characterizing novel material that can be used as energy storage and diffuser in constructing flat plate solar collector. Materials used are clay and granite dust obtained from Okelele and Kulende Quarry sites, both in Ilorin, Kwara State, Nigeria. The materials were sun-dried; the clay crushed before the two materials were sieved into different particle sizes. They were thereafter blended into different ratios and then characterized for thermal, physical and mechanical properties. Results showed that the highest thermal conductivity, thermal diffusivity and compressive strength were obtained from sample of particle size 0.075 mm and clay: granite ratio 50:50 (0.268176 W/mK, 3.58514 10–4 m2/sec and 3.571 N/m2, respectively). This same blend has a density of 0.91 g/cm3 and specific heat capacity of 824 J/kgK. This sample, having the optimal thermal, physical and mechanical properties will be a good replacement for conventional insulating materials currently being used for solar flat-plate collector construction as it will serve as both energy storage and diffuser. Keywords:    Solar energy; solar collector; insulating material; clay; granite dust; thermal conductivity; thermal diffusivity  
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.5
      Issue No: Vol. 48, No. 2 (2022)
       
  • Comparison on Vegetation Composition and Structure in Fire Prone Forest of
           Ilunde and Fire Suppressed Forest of Kitwe in Tanzania

    • Authors: Nyatwere D Mganga
      Pages: 294 - 303
      Abstract: Fire is among the factors influencing survival and development of plants in ecosystems. This study was conducted in frequently burnt and fire suppressed miombo woodlands of Ilunde and Kitwe, respectively. Tree stem density, basal area and composition of plants were determined. The methods used involved recording the numbers of tree stems, diameter at breast height and classifying vegetation to species level. In Kitwe forest, mean stem density of 582.7 ± 52.90 stems ha– was higher than 356.8 ± 38.98 stems ha– which was recorded in Ilunde forest (t = 15.98, df = 29, p < 0.05). Similarly, a higher mean tree basal area of 16.14 ± 1.32 m2 ha– was recorded in Kitwe forest, while 8.54 ± 0.94 m2 ha– being recorded in Ilunde forest (t = 3.34, df = 14, p < 0.05). Czekanowski’s similarity coefficients for trees, shrubs and saplings, and herbs and grasses were 0.46, 0.34 and 0.22, respectively. Fire adapted species were recorded in Ilunde forest. Fire prone miombo woodland had lower tree stem density, basal area and dominated by fire adapted species. Similarity coefficient between the two forests was also low. Prescribed burning is recommended in miombo woodlands for sustainable species composition and tree structure. Keywords: vegetation; composition, structure, fire prone, miombo.
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.6
      Issue No: Vol. 48, No. 2 (2022)
       
  • Evaluation of Natural Radioactivity and Radiation Hazards of Soils around
           Petroleum Products Marketing Company using Gamma Ray Spectrometry

    • Authors: Dayo A. Ayeni, Festus M. Adebiyi
      Pages: 304 - 312
      Abstract: This study aimed at evaluating natural radioactivity and radiation hazards of soils around a petroleum product marketing company due to anthropogenic influences using gamma ray spectrometry. Top soils (5 cm deep) were collected from diverse locations inside the premises of the Company using standard analytical technique, while control samples were acquired at approximately 200 m from the study area. Mean activity concentrations of the radionuclides in the test soils were 89.36 Bq/kg for 40K, 92.1 Bq/kg for 238U and 10.95 Bq/kg for 232Th, which are more than that of control samples with statistically significant differences. Assessment of the radiological levels of the oil-contaminated soils were done using internal hazard index, external hazard index, annual gonadal dose equivalent, annual effective dose rate, radium equivalent, total absorbed dose rate and representative level index (IŸ). The results showed that mean annual equivalent dose rate of the oil-contaminated soil (0.46 mSv/yr) fell below the permissive annual dose limit (1.0 mSv/yr). Mean internal hazard index (0.55 Bq/kg) and external hazard index (0.30 Bq/kg) values were less than the minimum permissible limit (1.0). Mean annual gonadal dose equivalent value (358.46 µSvy-1) of the radionuclides was close to the world average of 300 µSvy-1, while the mean representative gamma index value (0.78) was also less than unity. Estimated mean value (114.65 Bq/kg) of the radium equivalent was also below the world average of 370 Bq/kg, the values are also more than that of the control samples. Though the soils exhibited low gamma radiation, however lengthy term exposure may pose an inherent cancerous ill-health. It is vital to repeat this investigation periodically to avert precarious effects of anthropogenic influences; also indiscriminate discarding of oils should be discouraged. Keywords:    Gamma ray spectrometry; radionuclide; refined petroleum products; risk assessment; soil.
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.
      Issue No: Vol. 48, No. 2 (2022)
       
  • Exploring Carrier Sense Multiple Access with Collision Avoidance
           Techniques for Resource Sharing in Broadband Power Line Communications

    • Authors: Godfrey Luwemba, Mussa M. Kissaka , Prosper Mafole
      Pages: 313 - 323
      Abstract: A resource sharing in power line communications (PLC) for the home network is restricted by the channel assignment techniques which decide who has the right to gain access to send data. The channel assignment techniques include contention-free and contention-based. The former requires high synchronization due to the deterministic round-trip time. Besides, contention-based utilizes CSMA/CA techniques that allow stations in a network to compete for channel access and are suitable for decentralized network topology. However, a trade-off exists between the number of stations required to gain access versus system efficiency. Whilst some research has been carried out on CSMA/CA resource sharing techniques that allow only one user to transmit, there is very little work done on multiuser access to optimize system efficiency and reduce collisions in a network. The purpose of the current study was to review the CSMA/CA techniques for resource sharing to improve system efficiency in power line communications. In carrying out this study, a systematic literature review methodology to evaluate different related works and determine the most suitable approach to allow multiuser channel access was used. The study further demonstrated the impact multichannel access has on system efficiency. In addition, the study provides recommendations for future research. Keywords: CSMA/CA; Medium access control; OFDMA; power line; resource sharing;
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.
      Issue No: Vol. 48, No. 2 (2022)
       
  • Factors Influencing the Choice of Place of Delivery of a First Child among
           Nigerian Women

    • Authors: Olakiitan I Adeniyi, Nathanael B Afolabi, Adesupo A Akinrefon, Ifeyinwa V Omekam, Ifeoluwa R Olonijolu
      Pages: 324 - 334
      Abstract: Among the factors responsible for maternal deaths in developing countries is complications during pregnancy and childbirth, and as such, the choice of place for delivery is vital as the quality of attention received can either aid or reduce the risks attached to child bearing. This study seeks to statistically model factors that determine the place of delivery in Nigeria among women of reproductive age taking into consideration possible nesting structure in the mode of data collection. A two-level hierarchical multilevel logistic model with the individual women as the lower level and the state of residence as the second level was applied to 2018 Nigeria Demographic Health Survey (NDHS) data. Results showed that the odd of choosing a government or private facility reduced by 58.6% and 85.9%, respectively. Women in the rural areas are 12% and 20% less likely to choose either a government or private facility, additional education increases the odd of choosing any of the two facilities against home delivery. Other significant variables were wealth index, religion, assistance during labour and the number of antenatal visits. Keyword: Place of delivery; Nesting; Multilevel Logistic Model; Odds and Antenatal Care
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.
      Issue No: Vol. 48, No. 2 (2022)
       
  • Weathering the Storm: Community Socio-Economic and Physical Vulnerability
           Assessment of Informal Settlements to Disasters in Arusha City, Tanzania

    • Authors: Herbert Hambati
      Pages: 335 - 351
      Abstract: Urban population growth has demonstrated a synergetic relationship with the growth of informal settlements and vulnerability to disasters in urban areas. This study employed Community Participatory Vulnerability Assessment (CPVA) to analyse vulnerability in informal settlements in Arusha City, Tanzania. The results show that a plethora of factors, including socio-economic and physical realities interact in complex non-linear ways to shape vulnerability to disasters in informal settlements in the city. The study shows that coping strategies of some individuals in informal settlements reinforce their risks to disasters. This is particularly demonstrated by the stones that are positioned on weak roof structures for protection, and which may potentially serve as projectiles in the event of storm. This quick-fix coping strategy, which results from short-sighted narrow conception of human relationship to the natural environment, may appear sustainable in the short-term. However, given the rising uncertainties of the future, it is unlikely to be sustainable. The study concludes that indigenous knowledge holds great potential in community responses to long term considerations regarding environmental hazards. The study also recommends that measures and strategies aimed at reducing disasters should address the whole set of issues leading to poverty and exposure disparities within the community. Keywords:    Assessment; vulnerability, disaster, informal settlements, Tanzania.
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.
      Issue No: Vol. 48, No. 2 (2022)
       
  • The Reconstruction of the Late Pleistocene and Holocene Vegetation
           Dynamics in Lake Eyasi Basin, Northern Tanzania

    • Authors: Pastory M. Bushozi, Cassian T. Mumbi, Veronica M. Muiruri, Musa S. Mwitondi
      Pages: 352 - 370
      Abstract: Lake Eyasi Basin of northern Tanzania plays a pivotal role in the study of human-environment interactions and in understanding human flexibility and adaptability through technological innovations over time and space. In this study, phytoliths from ancient soils and fossil pollen proxies from radiocarbon-dated sequences from Kisimangeda on the north-eastern edge of the Lake Eyasi Basin, are used to interpret trends in climatic changes recorded since the Last Glacial Maximum (LGM) to the present. We used pollen and phytolith abundances from a core that was recovered on the northern margin of saline Lake Eyasi at the depth of five metres. The application of principal component and cluster analysis, together with linear regression provides insight into dataset structure and grouping with reference to the modern comparative datasets that in turn allow us to classify the various palaeoenvironments and paleohabitats occupied by the late Later Stone Age, Pastoral Neolithic, and Iron Age inhabitants of Kisimangeda. The chronological order, pollen and phytolith records in the studied part of the basin signify palaeoenvironments analogous to the Somalia-Maasai bushland and grassland ecosystems of today. Keywords:  Palaeoenvironments; Late Pleistocene; Holocene; pollen; phytoliths; human adaptation
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.
      Issue No: Vol. 48, No. 2 (2022)
       
  • Chemical Constituents and Antimicrobial Evaluation of Selected Aloe vera
           Branded Commercial Products in Tanzania

    • Authors: Stephen S Nyandoro, Bahati F Kyando , Joan JE Munissi
      Pages: 371 - 382
      Abstract: Chemical compositions and antimicrobial activities of twenty-two Aloe vera branded commercial products in Tanzania, a case of marketed soaps, creams, lotions, petroleum jelly, toothpastes and hair conditioner products in Dar es Salaam, were investigated. Chemical compositions were analysed using gas chromatography-mass spectrometry (GC-MS) whereas antimicrobial activities were evaluated using agar dilution method against four bacteria species, namely Staphylococcus aureus, Escherichia coli, Klebsiella pneumoneae and Salmonella typhi) and two fungal species Candida albicans and Cryptococcus neoformans. The GC-MS analysis revealed the presence of seven non-polar constituents, namely methyl palmitate, 9-octadecenoic acid methyl ester, methyl stearate, tetratetracontane, hexacosane, and pentacosane and methyl tetradecanoate as the most common ingredients among the products. Eleven compounds were detected in both the commercial products and reference A. vera extracts. The commercial products AVC5 and AVL3 inhibited the growth of E. coli and S. typhi at minimum inhibitory concentrations (MICs) of 7.5 and 12.5% (v/v), respectively, whereas AVC2 and AVC5 inhibited the growth of C. albicans and C. neoformans at 5.0% (v/v). AVC6 had 7.5 and 15.0% (v/v) MICs for C. neoformans and C. albicans, respectively. Other commercial products and the reference A. vera extracts were inactive against the tested microbes at a screening concentration of 10.0 mg/mL.  Keywords: Aloe vera; Aloe vera branded commercial products; GC-MS; Antimicrobial
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.
      Issue No: Vol. 48, No. 2 (2022)
       
  • Potential Economic and Environmental Benefits of Faecal Sludge Derived
           Compost and Char Briquettes: The case of Dar es Salaam, Tanzania

    • Authors: Isabela T Mkude, Richard Kimwaga , Sara Gabrielsson
      Pages: 383 - 393
      Abstract: The concept of resource recovery, particularly from waste has recently gained much attention and popularity. The aim of this study was to quantify the potential economic and environmental benefits of recovering nutrients and energy from faecal sludge (FS). The empirical data were collected from three unplanned settlements of Dar es Salaam City at Keko, Kipawa and Manzese. Two scenarios were developed to recover nutrients and energy. The estimations of potential amounts of compost and char briquettes were performed by using the resource value mapping (REVAMP) tool. Results from REVAMP indicated daily economic benefits across the study areas ranging between 680 and 950 USD for energy and up to 7,000 USD for nutrients recovered, based on the faecal sludge composition. In general, FS derived compost was found more profitable than FS derived briquettes. The analyzed environmental benefits include saving the estimated to 5 hectares of forest area from being cut when substituting the use of wood charcoal with FS-derived briquettes. Since the composting process resulted to be more profitable option between the two, this study recommends the adoption and scaling up. However, guidelines and standards should be developed for proper practices. Keywords: Faecal sludge; resource recovery; resource value mapping; briquettes; compost; economic benefits; environmental benefits
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.
      Issue No: Vol. 48, No. 2 (2022)
       
  • Modelling Internet Traffic Streams with Ga/M/1/K Queuing Systems under
           Self-similarity

    • Authors: Judoka Popoola, Olusogo J Popoola, Oyebayo R Olaniran
      Pages: 394 - 401
      Abstract: High-intensity concurrent arrivals of request packets in Internet traffic can cause dependence of event-to-event-times of the requests being served, which causes non-memoryless, modelled with heavy-tail distributions unlike common known traffics. The performance of Internet traffic can be examined using analytical models for the purpose of optimizing the system to reduce its operating costs. Therefore, our study examined a Ga/M/1/K Internet queue class (Gamma arrival processes, Ga; with memoryless-Poisson service process, M; a single server, 1, and K waiting room) and proposed specific derivations of its performance indicators. Real-life data of a corporate organisation Internet server was monitored at both peak and off-peak periods of its usage for Internet traffic data analysis. The minimum ‘0’ in the arrival process indicates self-similarity and was assessed using Hurst parameter, H, and their (standard deviation). ‘H’ > 0.5 arrival process in the peak period only, indicates self-similarity. Performance of Ga/M/1/K was compared with various queuing Internet traffic models used in existing literatures. Results showed that the value of the waiting room size for Ga/M/1/K has closest ties with true self-similar model at peak-periods usage of the Internet, which indicates possible concurrent arrival of clients' requests leading to more usage of the waiting room, but with light-tailed queue model at the off-peak periods. Therefore, the proposed Ga/M/1/K model can assist in evaluating the performance of high-intensity self-similar Internet traffic.      Keywords: Internet traffic; self-similarity; Ga/M/1/K model; gamma distribution
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.
      Issue No: Vol. 48, No. 2 (2022)
       
  • Avian Use of Habitat Patches Dominated by Exotic Leucaena leucocephala or
           Native Tree Species in Urban Dar es Salaam, Tanzania

    • Authors: Chacha Werema, Charles Wilson
      Pages: 402 - 413
      Abstract: There has been an incursion of an exotic Leucaena leucocephala in disturbed areas and into habitat patches of native tree species in some areas in Tanzania. However, the impacts of this exotic tree on native biodiversity are not well understood. We assessed bird use of habitat patches dominated by L. leucocephala in comparison to patches of native tree species  at the University of Dar es Salaam main campus, Tanzania, by comparing bird species richness, abundance and diversity using mist netting. Based on the same mist netting efforts in each habitat patch type, patches of native trees had significantly higher overall diversity (t = 1.999, df = 293.64, p < 0.05) and abundance (χ2 = 40.525, df = 1, p < 0.001) of birds than those dominated by the exotic L. leucocephala and significantly greater abundance of forest-dependent species (χ2 = 10.938, df = 1, p < 0.001) and forest visitors (χ2 = 15.258, df = 1, p < 0.001). The similarity in bird species between the two habitats was 0.658 indicating that many bird species occurred in both habitat types. The lower diversity and overall abundance of  birds in the patches dominated by the exotic plant suggest that it does not provide appropriate habitat for many bird species, and further spread of this exotic will be detrimental to the local avifauna. Keywords: Birds, diversity, native tree species, exotic tree species, Leucaena leucocephala.
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.
      Issue No: Vol. 48, No. 2 (2022)
       
  • A Mathematical Model and Sensitivity Analysis of Lassa Fever with Relapse
           and Reinfection Rate

    • Authors: Latifat M Erinle-Ibrahim, Olukayode Adebimpe, Waheed O Lawal, Joshua O Agbomola
      Pages: 414 - 426
      Abstract: In this research paper, we depict an unprecedented four-dimensional ordinary differential equation modeling the dynamic transmission of the Lassa fever virus incorporating relapse and reinfection rate. Recent studies showed that the recovered individuals from Lassa fever can again be susceptible; which contradicted the common assumptions made by different researchers on modeling of Lassa fever. So, this article corrects and states the implications of the assumptions on the population density. The numerical simulations unveil the effect of relapse, reinfection, and treatment rate in the affected population. Performing sensitivity analysis suggests all new incorporated parameters can impact the infection dynamics substantially. The stability analysis was carefully estimated where expression for each compartmentalized variable was calculated at both disease-free and persistence (endemic) equilibrium. Also, the basic reproduction number of the novel model was calculated using the Next Generation Matrix. The analytical results justify that the persistence (endemic) and the disease-free equilibrium are locally and globally asymptotically stable using both Routh Hurwitz Criterion and Comparison Theorem. Keywords: Lassa fever, Reinfection rate, Relapse rate, Treatment rate, Sensitivity analysis.  
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.16
      Issue No: Vol. 48, No. 2 (2022)
       
  • Toxicity Assessment of the Crude Ethanolic Pod Extract of Swartzia
           madagascariensis Desv. in Rats

    • Authors: Adelina A. Mwakalila, Saada M. Mbepera, Shaabani A. Mshamu, Amina Msonga, Washa B. Washa
      Pages: 427 - 434
      Abstract: This study assessed toxicity of the crude ethanolic pod extracts of Swartzia madagascariensis Desv in Wistar rats. Forty (40) Wistar rats aged 8–10 weeks were orally administered with crude extracts from pods of S. madagascariensis. Chemical analysis of serum and histopathology of liver and kidney from test animals were performed to determine the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and creatinine in serum. In addition, serum albumin levels were also determined. The levels of ALT, AST and creatinine were found to be high in groups treated with crude extracts compared to the control group, suggesting some damage in liver cells and kidney of treated groups of Wistar rats. The albumin levels in serum samples of crude extract treated groups were found to be low compared to control group, suggesting some leakage to the urine due to damage in the kidney. Histopathological analyses revealed damages in the liver and kidney treated with 1000 mg/kg of crude ethanolic pod extracts of Swartzia madagascariensis (CEPES) at days 2 and 14, corresponding to what was observed in the biochemical variables. The findings revealed that Swartzia madagascariensis pods are toxic once taken in large quantities (1000 mg/kg). Keywords: Toxicity, Wistar rats, Histopathology, biochemical parameters
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.17
      Issue No: Vol. 48, No. 2 (2022)
       
  • Effects of Temperature and Salinity on Incubation Time, Hatching Success,
           and Larvae Survival of the Giant Tiger Prawn Penaeus monodon under
           Experimental Conditions

    • Authors: Sawadi Ndunguru, Marcelian Njau, Blandina Robert Lugendo
      Pages: 435 - 446
      Abstract: Prawns are commercially one of the most important marine resources. However, in their early developmental stages, they face challenges related to physico-chemical and environmental changes. This study aimed at investigating the effects of temperature and salinity on egg incubation time, hatching success, larval and postlarval survival of the giant tiger prawn, Penaeus monodon (Fabricius 1798) obtained from the coastal waters of Tanzania. The adult females P. monodon collected off Rufiji delta were left to acclimatize and spawn at 28.5 ± 0.5 °C and 32 ppt in the hatchery. Spawned eggs were incubated at experimental temperatures of 27 °C, 31 °C and 35 °C with three subgroups of salinities of 30 ppt, 35 ppt and 40 ppt. The incubation time was longest (15.2 hours) at 27 °C and 30 ppt, and shortest (10.7 hours) at 35 °C and 40 ppt. Hatching success was highest (85.2%) at 31 °C temperature and 30 ppt salinity, and lowest (69.45%) at 35 °C and 40 ppt. Larval and postlarval survival was suitable at 27–31 °C and 30–35 ppt. These findings suggest that optimum rearing temperature and salinity for P. monodon range 27–31 °C and 30–35 ppt, respectively. Changes in temperature and salinity above the optimum range may jeopardize the hatching and subsequent survival of P. monodon especially at their early developmental stages which are more sensitive to environmental changes. Keywords:    Penaeus monodon, Temperature, Salinity, Incubation time, Hatching success, Survival rate.
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.18
      Issue No: Vol. 48, No. 2 (2022)
       
  • Effects of Feed Moisture Content, Soybean Ratio and Barrel Temperature on
           

    • Authors: Robert Mugabi, Stellah Byakika , Ivan Muzira Mukisa
      Pages: 447 - 459
      Abstract: The effects moisture content, temperature and soybean ratio on expanded product characteristics of extruded maize-soybean blends were studied. Response surface methodology was used to study the effects of extrusion conditions on extrudate properties taking barrel temperature (BT), feed moisture content (FM) and soybean flour ratio (SR) as factors. Expansion ratio (ER), water absorption index (WAI), water solubility index (WSI), hardness and colour (b* - (+) yellowness) of the extrudates were determined. BT and FM had significant effects on ER (p < 0.05). At low FM levels, ER increased with BT. It was observed that both FM and BT significantly affected WAI and WSI. WAI increased as FM increased. Increasing FM to 20% resulted in a decrease in WSI, beyond which an increase was observed. Hardness increased significantly as feed moisture content increased. High SR content significantly increased the extrudate hardness. FM had no significant effect on colour. Colour increased as the SR and BT increased. Significant regression models explained the effects of SR, FM, and BT on all response variables. All of the response variables' R2, were higher than 0.89. Keywords: Maize, Soybean, moisture content, extrusion.
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.19
      Issue No: Vol. 48, No. 2 (2022)
       
  • Charcoal Whirlwinds and Post-Fire Observations in Serengeti National Park
           Savannahs

    • Authors: Colin J. Courtney Mustaphi, Heleen C. Vos, Rob Marchant , Colin Beale
      Pages: 460 - 473
      Abstract: Whirlwinds and visible dust devils occur over semi-arid ecosystems and entrain particles from the ground surface. Fires produce abundant charcoal across savannahs and the resulting blackened surfaces create a large albedo contrast. Whirlwinds have been observed associated with active fires; yet, there are few published observations on post-fire landscapes. Spatiotemporal patterns of whirlwinds have been documented for a limited number of regions and have not been made for the ecosystems of eastern Africa. From field-based sightings in the Serengeti National Park, Tanzania, we report on whirlwinds over burned savannah patches that entrained large quantities of charcoal to produce black coloured charcoal devils that lofted charcoal into the atmosphere. Two occurrences of charcoal devils were sighted and photographed, one each in the Western Corridor (Bunda District) and Lamai (Serengeti District), Mara Region. The observations were compared with regional scale meteorological data and remote sensing satellite imagery and albedo estimates of the land cover conditions. Although direct meteorological or particulate matter measurements were not made, the observations show that both charcoal devils differed in colour, funnel shape, height, and savannah land cover types (different woody to grass fuel canopies), and thus different charcoal morphologies. Charcoal laden whirlwinds require further study and characterization to analyse the contribution to local-scale redistribution of matter and regional-to-global fluxes of terrestrially derived atmospheric particulates. Future research focusing on the spatiotemporal patterns of whirlwinds over burned patches of savannah, the formation, duration and dissipation mechanisms, and characterisation of the entrained material would contribute to our understanding of the phenomena. The redistribution of organic and clastic material would contribute to understanding of detrital fluxes to depositional environments, such as lakes, wetlands, and snow. Keywords:    Atmospheric boundary layer; Convection; Detritus; Dust devils; Fires; Particulate matter.
      PubDate: 2022-06-17
      DOI: 10.4314/tjs.v48i2.20
      Issue No: Vol. 48, No. 2 (2022)
       
 
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