2647 research outputs found
Sort by
Ionic liquids based on 1-ethyl-3-methylimidazolium cation and anions of tetrafluoroborate and bis(trifluoromethylsulfonyl)imide: Structural and thermodynamic properties by DFT study
No full textThis research article published by Elsevier B.V., 2020The theoretical study of neutral ion pairs of 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]) has been performed. The formation of the neutral ion pairs was considered through inter-ionic reactions involving the [EMIM]+ cation and two anions, [BF4]− and [NTf2]−. Computations were executed by the DFT/6-311++G(d,p) method with B3LYP5 and CAM-B3LYP functionals. The thermodynamic characteristics of the inter-ionic reactions have been determined theoretically for both ion pairs. The thermodynamic stability of the ion pairs was interpreted through analysis of the frontier molecular orbitals (FMOs). In addition, following experimental data available in literature for [EMIM][NTf2], the enthalpy and entropy of the reaction were obtained
Assessing the potentials of agricultural ecosystem pollination services to improve bean yield in smallholder farming systems
Get PDFA Thesis Submitted in Partial Fulfilment of the Requirements for the Degree of Doctor of
Philosophy in Life Sciences of the Nelson Mandela African Institution of Science and
TechnologyPollination services by insects contribute to production in 75% of food crop species. When
promoted through agro-ecological intensification (AEI), pollination can narrow yield gaps in
smallholder farming systems. The study evaluated the contribution of insect pollinators on
common beans (Phaseolus vulgaris L.) yields, and the knowledge gaps pre and post-training of
smallholder farmers (n=300) in pollinators and field margins in a bean agro-system were
investigated. Also, the role of field margin as a refuge for flower-visitors, and how plants and
pollinator richness and diversity can influence strength of pollination networks in three agro
ecological zones were investigated. Baseline and end-line surveys, pollinator exclusion and
fluorescent dye-experiments, insects and vegetation surveys were carried out to obtain data for
each specific objective of the study. While the majority of farmers were unaware of pollinators
and their importance as pollinators before training, the end-line survey one year after training
showed an increase in knowledge. The majority of farmers subsequently recognized honeybees,
hoverflies and solitary bees, by names and their role as crop pollinators and natural enemies (for
the case of hoverflies). Higher yield based on pods per plant and seeds per pod on open pollinated
and hand pollinated flowers were significantly recorded compared with plants from which
pollinators had been excluded suggesting that pollinators contribute significantly to crop yield.
Similarly, it was found that field margin plants are essential in supporting higher number of
pollinator taxa and can influence their richness in adjacent bean field. Collectively these results
showed that improving understanding among smallholder farmers of ecosystem services and their
ecological requirements are both feasible and essential for conservation of insect pollinators, which
are important for optimising yield in this production system, and that crop margin vegetation
provides habitat for these ecosystem service providers. Field margins with high plant diversity
displayed extended and more robust pollination networks compared to those with low plant
diversity, and consequently these habitat strips should be managed with sensitivity for pollinating
insects and for the stability and persistence of plant-pollinator interactions in this agro-system
Potential of probiotics from fermented cereal-based beverages in improving health of poor people in Africa
Get PDFThis research article published by Springer Nature Switzerland AG., 2020Milk and milk products; particularly yoghurts have almost exclusively been used as media for probiotic delivery to human being for a very long time. Despite health benefits such products have to humans; that include supply of nutrients, prevention and cure of certain communicable and non-communicable diseases; the presence of allergens, increased lactose intolerance, hypercholesterolemia effects, the need for vegetarian probiotic products, cultural food taboos against milk, and religious beliefs have led to limitations on the use of milk and its products as probiotic vehicles in many places including Africa. Such limitations have led to more researches worldwide on alternative delivery media for probiotics in order to meet the food preferences and demands of people affected by milk and milk products. An integrative approach has been used to find common ideas and concepts from different studies. Different food matrices have been tested for their ability to carry probiotics and cereals and cereal products have been found as among suitable substrates for the purpose. Some investigations have revealed that traditional African fermented cereal-based beverages are potential probiotic carriers because of the probiotic Lactobacillus spp. and yeasts which are involved in the fermentation of such products. This offers an opportunity for the African cereal beverages to be used to provide probiotic health benefits to the majority of African populations. Thus, this review provides information on probiotics including sources, types, health benefits, vehicles for their delivery and specifically also on challenges and future prospects for cereal-based probiotics development and consumption in Africa
The neuroimaging magnitude of pediatric brain atrophy in northern Tanzania
Get PDFThis research article published by The Pan African Medical Journal, 2020Introduction: the loss of parenchymal brain volume per normative age comparison is a distinctive feature of brain atrophy. While the condition is the most prevalent to elderly, it has also been observed in pediatric ages. Various causes such as trauma, infection, and malnutrition have been reported to trigger the loss of brain tissues volume. Despite this literature based knowledge of risk factors, the magnitude of brain atrophy in pediatric age group is scantly addressed in most developing countries including Tanzania. The current study aims to understand the magnitude of brain atrophy in children residing in Northern Zone, Tanzania.
Methods: a cross-sectional hospital survey was performed in which 455 children who were presented with various brain pathologies from the year 2013 to 2019 and whose brains examined by Computerized tomography (CT)-Scanners were recruited in the study. The brain statuses were examined using three linear radiological methods including the measure of sulcal-width, Evans index, and lateral ventricular body width.
Results: results showed a significant number of atrophied brains among children in Northern Tanzania and that the condition was observed to have a 1:1 male to female ratio. The prevalence of pediatric brain atrophy was found to be 16.04%.
Conclusion: the cortical subtype of brain atrophy presented as the most prevalent type of brain volume loss. The findings of this study suggest existence of considerable trends of brain atrophy in children which need special attention and mitigation plans
A mathematical model to inform on desirable dog-rabies control methods in an urban setting: a case study of Arusha-Tanzania
Get PDFDissertation Submitted in Partial Fulfillment of the Requirements for the Degree of
Master’s in Mathematical and Computer Science and Engineering of the Nelson
Mandela African Institution of Science and TechnologyRabies is a zoonotic, viral disease that causes an acute brain inflammation in mammals. It is
transmitted through the saliva of infected animals via bites, scratches or contact with infectious
tissue. In this study, we formulate a deterministic model which measures the effects of culling
and vaccination on dog mediated transmission of rabies for urban areas near wildlife, using the
Arusha region as an example. Various parameter values were deduced from five years worth
of survey data on Arusha’s dog population and dog vaccination coverage from the Mbwa wa
Africa group, a Non Governmental Organisation and from records of dog bite incidence and
deaths cases from the Ministry of Livestock and Fisheries, Tanzania. Three distinct dog populations
were assumed: domestic dogs, stray dogs and Pastoralist dogs. The basic reproduction
number R
0
and effective reproduction number R
for rabies were computed to estimate transmission
and found to be 1.9 and 1.2 respectively. The disease free equilibrium "
e
was also
computed. When R
< 1 it implies that it is globally asymptotically stable in the feasible region
. When R
e
e
> 1, it implies that, there is an equilibrium point which is endemic and locally
asymptotically stable. According to the sensitivity indices, infection rate of stray dogs
is the
most positive sensitive parameter and natural death rate of stray dogs
is the most negative
sensitive parameter. This study proposes putting much emphasis on the most positive and most
negative sensitive parameters when fighting against dog-rabies transmission in urban areas near
wildlife reservoirs. Under the assumption that a dog is immune to rabies for 3 years once vaccinated,
the numerical simulations of the formulated model predict that the number of infected
stray dogs will increase to its highest in 2020. However, the number of infected domestic dogs
is expected to decline to its minimum in 2020, while the number of infected Pastoralist dogs will
stay similar the same as the previous years in 2020. These results show that, rabies incidence
for the infected stray dogs is the highest followed by the incidence for infected Pastoralist dogs
and lastly for the infected domestic dogs. The numerical simulation of the reproduction number
shows that dog mass vaccination is the most appropriate method in the long term to control
rabies transmission among dog sub-populations for urban areas near wildlife reservoirs such as
Arusha. Culling on the other hand, is effective at the moment in time when it is practiced, but
its protective effect quickly decreases after just 6 to 8 months when all culled dogs will have
been replaced by un-vaccinated new born puppies
Numerical Analysis of Heat Exchanger for Spray-Assisted Low-Temperature Desalination System
Get PDFThis research article was published by Hindawi in 2020A numerical study for heat exchanger for spray-assisted low-temperature desalination system is presented for an existing low-temperature desalination unit at Arusha Technical College. This is aimed at recognizing the effect of mass flow and physical parameters like tube layout (diameter and length) on the overall heat transferred and the pressure drop in the shell-and-tube heat exchanger (STHX), as well as the impact of these parameters on the heat transfer coefficient and the overdesign of the STHX. Also, the study provides a suitable mathematical model for the replacement of the current condensation unit which tends to reduce energy consumption by reducing some of the electrical components in the system. A Math CAD model was developed using the Delaware method to obtain the mentioned parameters. The results show that at 0.8 kg/s flow rate a maximum heat transfer coefficient of 23212 W/m2K is achieved in a minimum diameter of 10 mm within a maximum tube length of 1000 mm heat exchanger and the pressure drop seems to be very low in a range of 0.328-0.957 Pa from all configurations. The configuration with 1000 mm tube length and 10 mm diameter performed well on the mass flow of 0.3 kg/s-0.8 kg/s by providing a suitable overall heat transfer coefficient of 2306-2539 W/m2K, while 12.8 is a maximum overdesign coefficient achieved on 0.8 kg/s mass flow. The study results show the possibility of using STHX instead of the current condensation unit in implementing a proposed system layout with the minimum effect of energy consumption
Experimenting with local electricity markets in China – multilevel drivers and barriers in the sociotechnical regime
Get PDFThis research article published by Elsevier Ltd., 2020As part of its market reforms in the energy sector, the Chinese central government introduced local electricity market pilots in 2019. Through the integration of renewable resources and the possibility for consumers to participate, local electricity markets not only support the centralized electricity grid, but also form a new alternative for electricity distribution. Based on the socio-technical transition theory, this paper aims to present a multi-level perspective on local electricity markets in China and to identify drivers and barriers to their implementation. The Chinese government's “experimental governance” strategy is identified as niche management for local electricity markets and therefore as an important driver for the market development. However, the current state of the socio-technical regime with its is characterized by rigid structures has created some barriers that can only be partially overcome by new opportunities that arise in the niches
Potential of anaerobic co-digestion in improving the environmental quality of agro-textile wastewater sludge
Get PDFThis research article published by IWA publishingSludge from textile effluent treatment plants (ETP) remains a challenge for many industries due to inefficient and limited waste management strategies. This study explores the potential of using anaerobic digestion (AD) to improve the environmental quality of textile ETP sludge. The AD of ETP sludge is affected by the low C/N ratio (3.7), heavy metal content, and toxicity. To improve the process, co-digestion of ETP sludge with different substrates (sewage sludge, cow dung, and sawdust) under mesophilic conditions (37 °C), followed by a thermochemical pretreatment was assessed. The results showed that anaerobic co-digestion of the textile sludge with the co-substrates is effective in reducing pollution load. It was found that organic matters degraded during the 30-day AD process. The chemical oxygen demand and biological oxygen demand reduction was in the range of 33.1–88.5% and 48.1–67.1%, respectively. Also, heavy metal (cadmium, lead, iron, and, mercury) concentration was slightly reduced after digestion. Maximal biogas yield was achieved from co-digestion of textile sludge and sewage sludge at a mixing ratio of 3:1, 1:1, and 1:3, and methane content was respectively 87.9%, 68.9%, and 69.5% of the gas composition. The results from this study show that co-digestion will not only reduce the environmental pollution and health risks from the textile industry but also recover useful energy
Quantifying nutrient re-distribution from nutrient hotspots using camera traps, indirect observation and stable isotopes in a miombo ecosystem, Tanzania
Get PDFThis research article published by Elsevier B.V., 2020Nutrient hotspots strongly attract mammalian herbivores in nutrient-poor habitats such as
savanna systems. However, little is known about their seasonal importance for mammalian
herbivore species, particularly grazers. In addition, no study has fully quantified the potential re-distribution of nutrients into the surroundings of these hotspots. We assessed
nutrient hotspot (i.e., grazing lawns and termite mounds) use by herbivores in a Miombo
ecosystem of the Issa valley, Tanzania, using dung counts, camera traps and stable isotope
analyses over a one year period, from May 2016 to October 2017. We conducted dung
counts along four transects each radiating away from ten termite mounds and six grazing
lawns as well as in 16 control sites 100 m away from each nutrient hotspot. In addition, we
sprayed grasses around five termite mounds with urea and traced the isotopic signature
back in grazing herbivore dung. Grazer dung deposition was twice as high in hotspot areas
vs control sites. A total of 32 camera stations recorded 244 wildlife encounters, with
mammalian herbivores using hotspot areas four times more frequently compared to
control plots. Stable isotope analyses highlighted that dung deposited by mammalian
grazers around hotspots likely originated from grasses within or close to hotspot areas,
indicating that grazers are responsible for maintaining nutrient stability of these hotspots.
We, therefore, emphasize the importance of grazing mammal species for the long-term
persistence of hotspots and, thus, their contribution to the maintenance of a heterogeneous landscape within the Miombo ecosystem
Sniffing Oriental Aromatic Scents: The Perfumery Trope in Eroticized Swahili Odes.
Get PDFThis Research Article was published by the Journal of the Institute of Kiswahili Studies University of Dar es Salaam Kiswahili, Vol. 84(2), 2020Swahili poets of the eighteenth and nineteenth centuries have foregrounded
adapted perfumery customs with great reverence in their works. It functions as a
vital cue to trans-Indian Ocean commonalities and as a marker of the influence
of Arabian-Manga civilisation and perfumery practices on the Swahili customs.
This paper examines the culture of scent in selected poetic works attributed to
Fumo Liyongo and Mwana Kupona Mshamu. Interestingly, the geography of
the female body parts is fused with oriental scents to excite consensual romantic
intimacy. We argue, besides historically echoing the sensuousness of oriental
perfumery in Swahili culture, that these two poets subliminally de-odorise body,
mind and soul of their readers to experience imagery of passionate intimacy.
Specifically, this article intends to focus on two prominent motifs of cross-
cultural adornment: the use of Manga attar unguent, fragrance and perfume, and
the scenting of genitalia. The article confronts these postulations concretised on
an approach based on Georges Bataille’s theory of eroticism. According to Carl
Olson, Bataille was an influential French postmodern thinker and writer who
argued that human life could best be understood by the interconnections and
workings of eroticism (1994:231-250). He mixes philosophy and anthropology
to talk about eroticism. According to Minguy, Bataille, through erotic
transgressions, saw the possibility for true human freedom and communication.
This theory, therefore, guides our arguments and counter-arguments,in the present article. It is the fulcrum upon which our discussions are premised