2647 research outputs found
Sort by
Bionomics of the African Apefly (Spalgis lemolea) as A Potential Natural Enemy of the Papaya Mealybug (Paracoccus marginatus) in Tanzania
Get PDFThis research article published by MDPI, 2020The African apefly (Spalgis lemolea Druce) is a potential natural enemy of the papaya mealybug (Paracoccus marginatus Williams and Granara de Willink). We studied the life history of apeflies in the laboratory at a temperature of 25–27 °C and a relative humidity of 55%–65% under a 12 h photoperiod condition. The papaya mealybugs and apefly larvae were collected from papaya plants in Tengeru, Arusha, Tanzania. The papaya mealybugs were introduced and allowed to multiply on potted sprouting potato plants in screened cages. In order to study the life cycle and predation of apeflies, an apefly egg was placed on an open screen-covered petri dish containing a moist blotter paper and observed for larva emergence. After the apefly larva emergence, a mixture of mealybug eggs (up to 1500), nymphs (200–250) and adults (100–150) was introduced in the petri dish each day and the consumption rate by the apefly larvae was quantified until the larvae reached pupal stage. Then, the apefly adults were collected and put into cages 30 cm × 30 cm × 30 cm containing cotton wool soaked in water, for observation of pre-mating, mating, egg-laying and life span. Results indicate that the apefly completed its life cycle in 23 days. The mean development period of the eggs was four days and the development period for the larva, pre-pupa, and pupa was nine, one and ten days respectively. The adult apefly emerged after 9 days of the pupa stage with mean body lengths of 10.1 ± 0.4 mm and 11.0 ± 0.8 mm for the males and females, respectively. The female laid an average of 68 eggs in groups of two to seven at different sites after 4–5 days of emergence. In this study one apefly larva was capable of consuming about 1983 ± 117, 123 ± 6 and 80 ± 9 papaya mealybug eggs, nymphs and adults respectively during larval stage. These results reveal the predatory potential of the apefly in suppressing the population of papaya mealybugs under field conditions
A two-way electricity usage monitoring system for decentralised solar mini-grids in Tanzania
Get PDFA Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of
Master’s in Information and Communication Science and Engineering of the Nelson
Mandela African Institution of Science and TechnologyDecentralised solar mini-grids have been identified as a cost-effective solution towards
having sustainable electrification efforts in Tanzania, particularly to areas out of the
government’s immediate plans for national grid extension. Nonetheless, access to information
on power consumption to both mini-grid companies and consumers has been a challenge for
most of the current decentralised solar mini-grid systems. Several studies, mostly carried out
outside Africa, have attempted to address the problem, however, due to the technology used,
features and economic implications, the proposed solutions do not suit the local market.
With the rapid penetration of information and communication technologies services in
Tanzania, access to and the use of the internet is becoming increasingly affordable for the
majority of communities. This study therefore aimed at improving consumer and utility
companies' access to electricity consumption information in decentralised solar mini-grids in
Tanzania. This was achieved by developing a two-way electricity usage monitoring system
that enhances consumers awareness towards economic utilisation of the available electrical
power resources. The proposed system uses Long Range technology to create a private Low
Power Wide Area Network around the mini-grid centre while General Packet Radio Service
network is used to transmit power consumption data from the mini-grid centre to the cloud
server.
The proposed system can help consumers to have informed-usage of electrical power and
thus adjust their consumption behaviour to save unnecessary costs. The system also offers a
cost-effective solution for the mini-grid companies to track the demand and supply status of
the available power resources. The system also acts as a linkage between mini-grid
companies and consumers which improves customer experience. Moreover, this study
contributes to the existing literature by proposing an improved method to enhance equal
access to the information regarding power consumption between utilities and consumers by
using Long Range as a private wide area network for the mini-grid centres
Determining tributary sources of increased sedimentation in East-African Rift Lakes.
Get PDFThis research article published by Elsevier B.V., 2020Temporal and spatial sediment dynamics in an East-African Rift Lake (Lake Manyara, Tanzania), and its river inputs, have been evaluated via a combination of sediment tracing and radioactive dating. Changes in sedimentation rates were assessed using radioactive dating of sediment cores in combination with geochemical profile analysis of allogenic and autogenic elements. Geochemical fingerprinting of riverine and lake sediment was integrated within a Bayesian mixing model framework, including spatial factors, to establish which tributary sources were the main contributors to recent lake sedimentation. The novel application of Bayesian source attribution on sediment cores and subsequent integration with sedimentation data permitted the coupling of changes in the rate of lake sedimentation with variations in sediment delivery from the tributaries. These complimentary evidence bases demonstrated that Lake Manyara has experienced an overall upward trajectory in sedimentation rates over the last 120 years with distinct maxima between 0.80 and 0.85 g cm yr in the 1960s and between 0.84 and 1.81 g cm yr in 2010. Increased sedimentation rates are largely a result of a complex interaction between increased upstream sediment delivery following changes in land cover and natural rainfall fluctuations. Modelling results identified two specific tributaries as responsible for elevated sedimentation rates, contributing 58% and 38% of the recently deposited lake sediment. However, the effects of sedimentation were shown to be spatially distinct given the domination of different tributaries in various areas of Lake Manyara. The application of source-tracing techniques constrained sedimentation problems in Lake Manyara to specific tributary sources and established a link between upstream land degradation and downstream ecosystem health. This novel application provides a solid foundation for targeted land and water management strategies to safeguard water security and environmental health in Lake Manyara and has potential application to fill knowledge gaps on sediment dynamics in other East-African Rift Lakes
Protocol for the trial to establish a causal linkage between mycotoxin exposure and child stunting: a cluster randomized trial.
Get PDFThis research article published by BMC Public Health, 2020Background: The number of stunted children has fallen globally but continues to increase in Africa. Stunting is
estimated to contribute to 14–17% of child deaths under 5 years of age and is a risk factor for poor cognitive and
motor development and educational outcomes. Inadequate dietary intake and disease are thought to be the
immediate causes of undernutrition and stunting. However, improving infant diets through complementary feeding
interventions has been shown to only modestly reduce stunting. Multiple observational studies demonstrate a dose
response relationship between fetal and post-natal aflatoxin exposure and reduced linear growth.
Methods: This community-based cluster randomized trial will measure the effect of a reduced aflatoxin diet on
length-for-age Z scores at 18 months in central Tanzania. All 52 health facilities in the Kongwa District of Dodoma
Region were randomized into two groups. Starting at 6 months of age, participants in the intervention group
receive a low-aflatoxin pre-blended porridge flour containing maize and groundnut (ratio 4:1 respectively) and lowaflatoxin groundnut flour, whereas in the control group the same porridge mix and groundnut flour are promoted
through education but acquired by the household. Both groups will receive the same infant and young child
feeding education and a thermos flask. A total of 3120 infants between 6 weeks and 3 months of age will be
recruited into the study over 1 year. Data will be collected four times – at recruitment and when the infants are 6,
12 and 18 months of age. In a cohort of 600 infants, additional data will be collected at 9 and 15 months of age.
The primary outcome is length-for-age at 18 months. Secondary outcomes include the Z scores for weight-for-age,
middle upper arm circumference and head circumference, and the blood biomarker aflatoxin-albumin in the full
sample, with the urine biomarker aflatoxin M1 analyzed in the cohort only.
Discussion: Better understanding the etiology of childhood stunting can lead to more appropriate interventions
and policies to further reduce linear growth faltering and meet the Sustainable Development Goal
Modelling and optimisation of water loss management strategies in a water distribution system: a case of Moshi Urban Water Supply and Sanitation Authority (MUWSA)
Get PDFA Dissertation Submitted in Partial Fulfilment of the Requirements for the Degree of
Master’s in Mathematical and Computer Sciences and Engineering of the Nelson
Mandela African Institution of Science and TechnologyWater loss in water distribution systems (WDS) is a serious problem in developing countries.
A lot of water is lost on its way from the sources before reaching the consumers due to leakage,
illegal use, and theft of infrastructures among others. The effect of water loss in the WDS
includes reduction of revenue, water shortage, disruption of water quality, and inflation of
operation and maintenance cost of the water authorities. The control of water loss in the WDS
is closely dependent on the commitment of the decision-makers, the strategies used and budget
set for water loss management (WLM).
This study presents a combined model of Multi-Criteria Decision Making (MCDM) and Integer
Linear Programming (ILP) methods which may help decision-makers to prioritise and select
the best strategies for WLM. The MCDM family methods; the MAVT, SMARTER, SAW, and
COPRAS were used to evaluate and prioritize the strategies, while ILP was used to select the
best strategies. Additionally, the study compared the SAW and COPRAS methods in
prioritising and selecting the strategies. The data used were collected at MUWSA.
The results show that the COPRAS and SAW methods rank the given alternatives differently
while when integrated with the ILP technique, the formulated models select the same portfolios
of alternatives. Thirteen alternatives which cost 97% of the total budgets set for WLM were
selected. Furthermore, the ILP models showed robustness in selecting the portfolio of
alternatives as they select the same alternatives despite the ranking of alternatives and change
of weights of evaluation criteria.
Finally, the study proposed the decision model framework which can be used by decisionmakers
to
evaluate
and
select
the
best
strategies
for
WLM
in
WDS
Assessment of the Knowledge, Perceptions, and Reactions towards the African Apefly (Spalgis lemolea lemolea) in Tanzania
Get PDFThis research article published by MDPI, 2020This paper reports on farmers’ knowledge, perceptions, and reactions towards the African apefly (Spalgis lemolea lemolea), which appeared to be associated with some vegetables in some locations in Tanzania. Information was obtained from a sample of 100 key respondents using a semi-structured questionnaire and from focus groups selected from key locations in five districts in the country with histories with the African apefly. Acute and sub-acute toxicity tests of the African apefly were performed on female Swiss hybrid mice (Mus musculus) to assess whether or not the African apefly was toxic to mammals. The mice were exposed to increasing apefly meal concentrations in acute and sub-acute tests, and signs of toxicity were observed for 14 and 28 days, respectively. Blood samples were collected by cardiac puncture for hematological and biochemical analysis. Gross and microscopic examinations of the internal organs were done. The survey results showed that 92.1% of the respondents perceived the African apefly as poisonous and had stopped consuming the vegetables associated with it. In the toxicity tests, however, no death or toxic signs were displayed, and there was no significant difference between the control and treated mice in weight, hematological parameters, and histo-pathological examination results. These findings strongly indicate that, despite the negative perception by farmers regarding the African apefly, it is not poisonous. However, further studies on how farmers can be trained to have a positive perception of the African apefly and how the insect can be conserved for further research regarding its role in Tanzania are recommended
Cryptogamic packed biofilter as potential adsorbent for co2, h2s and nh3 impurities from biogas
Get PDFA Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Master’s in Sustainable Energy Science and Engineering of the Nelson Mandela African Institution of Science and TechnologyThe presence of elevated concentrations of carbon dioxide, hydrogen sulfide, ammonia and trace impurities in biogas affect its caloric value as well as causes corrosion and are extremely toxic. There are various methods for removal of these impurities, but most are chemically based, expensive and limited in use. In this work, cryptogams (moss) integrated with soil and biochar packed in a filter have been employed for simultaneous removal of CO2, H2S and NH3, from biogas. Different soil types rich in metallic oxides at a different mass of (100 g, 150 g and 200 g) with a fixed mass of moss and biochar were tested in an on-site experiment to determine the removal efficiency (RE) and sorption capacity (SC). The adsorption dynamics of the filters were investigated at two flow rates, 80 ml/min and 100 ml/min, by determining removal efficiency. For the contribution of each substrate, sorption capacity and breakthrough time were determined by considering 5 g of each substrate that made up the filter. The soils with a high content of extractable cations showed excellent adsorption capacity for H2S by about 20 gS/100 g, which was higher than other adsorbents tested. It was found that integrated biofilter made up of bed arrangement of the soil, biochar and moss plant improved the quality of biogas with SC of 11 g-S and RE of 93% for H2S, 72% for NH3 and 68% for CO2.
Keywords: Cryptogams, Biofiltration, Biochar, Removal efficiency, Sorption Capacity
Enhanced electrosorption capacity of activated carbon electrodes for deionized water production through capacitive deionization
Get PDFThis research article published by Elsevier B.V., 2020The deionized water (DI) of high purity standards is used in several industrial processes to manufacture products and technologies for high end applications. Currently, DI water is produced by either reverse osmosis or continuous electrodeionization systems, however; both of them are facing several limitations. Therefore there is an urgent need for the alternative technologies for DI water production. This study investigated suitability of producing DI water by using capacitive deionization (CDI) with nitric acid treated activated carbon electrodes (NTAC). Activated carbon (AC) was etched in nitric acid solution to introduce various oxygen functional groups on its surface. The Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to confirm the increased surface oxygen containing groups on AC after nitric acid treatment that enhanced its salt adsorption capacity. CDI experiments were conducted using water solution of 12.0 μS/cm as a result DI water with the conductivity of 1.6 μS/cm (DI water grade III, according to International Organization of Standards) was produced. Also, electrochemical tests revealed good capacitive behavior due to improved conductivity with NTAC having highest specific capacitance of 381.7 F/g compared to 106.6 F/g of AC electrode. This study provides an insight of the electrosorption performance of materials in desalination of solutions of low ionic strength
Spatial distribution and insecticide susceptibility profile of aedes aegypti mosquitoes in south-eastern, Tanzania
Get PDFA dissertation submitted in Partial Fulfillment of the Requirements for the Degree of
Master of Science in Public Health Research of the Nelson Mandela African Institution of
Science and TechnologyAedes-borne diseases such as dengue and chikungunya constitute constant threats globally. In
Tanzania, the main vector species is Aedes aegypti, which is widely distributed in urban areas, but
whose ecology remains poorly-understood in growing towns and secondary cities. We collected
adult mosquitoes using Gravid Aedes trap and surveyed aquatic habitats of Ae. aegypti mosquitoes
in and around Ifakara, a fast-growing town in south-eastern Tanzania. Field-collected mosquitoes
were tested for susceptibility to common insecticides in dry and rainy seasons. A total of 926
mosquitoes were collected, 431 (46.5%) were identified as Aedes aegypti, 487 (52.5%) Culex, 8
(0.01%) as other Aedes and 13 (0.01%) as Anopheles mosquitoes. Of 1515 and 1933 aquatic
habitats examined in dry and rainy seasons respectively, 18.87% and 14.64% contained Aedes
immatures (container index. In the 2315 and 2832 houses visited in dry and rainy seasons, 4.9%
and 6.6% had at least one Aedes-positive habitat. The main habitat types included: (a) used vehicle
tires and discarded containers, (b) flower pots and clay pots, and (c) holes made by residents on
trunks of coconut trees to support climbing harvesters. Aedes aegypti adults were susceptible to all
tested insecticides in both seasons, except bendiocarb, against which resistance was observed in
rainy season. The high infestation levels indicate significant risk of Aedes-borne diseases,
requiring immediate action to prevent potential outbreaks in the area. While used tires, discarded
containers and flower pots are key habitats for Aedes, this study also identified coconut harvesting
as an important risk factor, and the associated tree-holes as potential targets for Aedes control.
Since Ae. aegypti mosquitoes are still susceptible to insecticides, effective control could combine
environmental management, preferably involving communities, habitat removal and insecticide
spraying
Peste des petits ruminants Virus Transmission Scaling and Husbandry Practices That Contribute to Increased Transmission Risk: An Investigation among Sheep, Goats, and Cattle in Northern Tanzania
Get PDFThis research article published by MDPI, 2020Peste des petits ruminants virus (PPRV) causes an infectious disease of high morbidity
and mortality among sheep and goats which impacts millions of livestock keepers globally. PPRV
transmission risk varies by production system, but a deeper understanding of how transmission
scales in these systems and which husbandry practices impact risk is needed. To investigate
transmission scaling and husbandry practice-associated risk, this study combined 395 household
questionnaires with over 7115 cross-sectional serosurvey samples collected in Tanzania among
agropastoral and pastoral households managing sheep, goats, or cattle (most managed all three,
n = 284, 71.9%). Although self-reported compound-level herd size was significantly larger in pastoral
than agropastoral households, the data show no evidence that household herd force of infection
(FOI, per capita infection rate of susceptible hosts) increased with herd size. Seroprevalence and
FOI patterns observed at the sub-village level showed significant spatial variation in FOI. Univariate
analyses showed that household herd FOI was significantly higher when households reported
seasonal grazing camp attendance, cattle or goat introduction to the compound, death, sale, or giving
away of animals in the past 12 months, when cattle were grazed separately from sheep and goats, and
when the household also managed dogs or donkeys. Multivariable analyses revealed that species,
production system type, and goat or sheep introduction or seasonal grazing camp attendance, cattle
or goat death or sales, or goats given away in the past 12 months significantly increased odds of
seroconversion, whereas managing pigs or cattle attending seasonal grazing camps had significantly
lower odds of seroconversion. Further research should investigate specific husbandry practices across
production systems in other countries and in systems that include additional atypical host species to
broaden understanding of PPRV transmission