2647 research outputs found
Sort by
Enhanced m-learning assistive technology to support visually impaired learners in Tanzania the case of higher learning institution
Get PDFA Dissertation Submitted in Partial Fulfilment of the Requirements for the
Degree of Doctor of Philosophy in Information and Communication Science and
Engineering of the Nelson Mandela African Institution of Science and TechnologyThe growing penetration of mobile and networked devices, for example, standard phones,
smartphones and tablets have gradually transformed the mode of teaching and learning in
Higher Learning Institutions (HLIs). The learning process is increasingly online, with
students using electronic devices to access content and to self-learn at any time and from
any place. This online ubiquitous learning is termed electronic-learning, or mobile learning
(M-learning) when mobile devices are used. In Tanzania, 36% of people aged 24-29,
which is the largest age group of students in HLIs, own a mobile device. As a result, m learning has been increasingly adopted by HLIs. However, little is known on the level of
engagement in M- learning by visually impaired learners (VILs) in Tanzania; for instance,
the tools they use and the challenges encountered when accessing learning contents. With
an estimated 250 VILs in Tanzanian HLIs, it is essential to ensure that the ever-increasing
reliance on electronic and mobile learning does not leave them with knowledge and skills
gaps, as these could contribute to poor performance, dropping out and lower chances of
employment after graduation. In this regard, assistive technology is needed in HLIs
because as the world shifts from traditional classroom settings to online settings, VILs
needs it in order to move with the pace and improve academic achievement.
This study is intended to determine the usability of existing versatile assistive technologies
among VILs in Tanzanian HLIs and the challenges that they face when accessing online
learning platforms. User requirements for assistive features were gathered, and an assistive
technology prototype was developed and validated. Data were collected via surveys and
interviews involving 33 VILs in four HLIs. The study found that 67% of respondents did
not know about mobile assistive technologies or integrated assistive technologies on online
learning platforms. Also, 66% could not afford smartphones and were therefore unable to
use assistive technologies. The prototype was developed for Android devices and consists
of three parts: a user management component for user authentication; a learning resources
component for a learning management system available in their HLIs; and a speech
synthesizer. Whereby the platform can be able to synthesizer text and graphical contents
into audio content, with the pitch analyzer. A usability test was conducted with 7 VILs
using the System User Scale (SUS) questionnaire. The prototype achieved an average
score of seventy-six-point eight percent (76.8%), which was higher than the 68% usability
score given to existing Android accessibility tools. It is confirmed that accessibility,
ii
knowledge and skills are the principal concern with respect to the adoption and usage of
learning technology for visually impaired learners
An eco-friendly tanning method using plant barks and their combination with aluminium sulphate from kaolin for leather industry
Get PDFA Thesis Submitted in Fulfillment of the Requirements for the Degree of Doctor of
Philosophy in Materials Science and Engineering of the Nelson Mandela African
Institution of Science and TechnologyChrome tanning has remained the most preferred tanning method worldwide in the leather
industry because it produces leather of a high quality with all the desired features. However,
environmental concerns of chromium shifted the focus of current research to chrome-free and
greener chemical processing options. When used in combination with some eco-friendly metal
salts, vegetable tannins are environmentally safe and manageable, while producing excellent
quality leather, bearing shrinkage temperature above 100 °C as that of chromium tanned leather.
As such, shortage of vegetable tannin supply requires characterization of non-commercialized
sources locally available in Tanzania for cottage tanneries. In the present work, vegetable tannins
from the stem barks of local plants namely Acacia mearnsii (A. mearnsii), Acacia xanthophloea
(A. xanthophloea), Euclea divinorum (E. divinorum) and root barks of Euclea racemosa (E.
racemosa) were prepared using a simple extraction technique at 30-80 °C. Extract yield, tannin,
total flavonoid and phenolic content, cross-linking ability as well as properties of the tanned
leather were determined. Results indicated that even at low temperature (50 °C) the barks yield
vegetable tannins with features similar to that of a commercialized source of tannin. Euclea
racemosa extract had low tannin, phenolic and flavonoid content and its crosslinking ability was
poor; hence, was determined as an un-suitable tannin source. Despite recording less extract
yield, tannin and other contents than that of A. mearnsii, the extract from E. divinorum bark
demonstrated a substantial tanning ability, which is attributable to its high tannin strength.
However, a broad interval between T
onset
and T
peak
of treated hide powder necessitated
combination tanning with aluminium sulphate [Al
2
(SO
4
)
3
] to lower the interval. About 2% (w/v)
aluminium oxide (Al
2
O
3
) equivalent is an optimal dose of Al
2
(SO
4
)
3
for extract pre-treatment.
Since the main source of Al
2
(SO
4
)
3
, bauxite, is diminishing in the world, an alternative source of
Al
2
(SO
4
)
3
was explored. The Al
2
(SO
4
)
3
was prepared from Kaolin of Pugu hill in Tanzania and
applied for combination tanning. The study has proven the suitability of kaolin as an alternative
source of Al
2
(SO
4
)
3
for combination tanning with vegetable tannins. Leather tanned with the
combination of the prepared Al
2
(SO
4
)
3
and vegetable tannin exhibited the shrinkage temperature
of up to 118 °C as compared to vegetable tannins alone that showed the average of 80 °C.
Mechanical strength characteristics met the standard norms. Fiber separation was good as
confirmed through microscopic studies. The study provides useful information and new insights
on accomplishing self-sustenance through available resources and an eco-friendly manufacturing
system for leather industries in Tanzania and beyond
Characterization of soil phosphate status, sorption and saturation in paddy wetlands in usangu basin-Tanzania
Get PDFThis research article published by Elsevier Ltd., 2021Phosphorus (P) is a vital plant macronutrient required for plant growth which usually available in
limited amount. P availability for plant uptake in highly weathered soil is controlled by soil erosion
and high fixation. The availability of P applied from fertilizers depend on the soil pH, soil sorption
capacity (PSC) and P saturation status (PSD), which determines P storage, losses, fixation, and
additional P to be added with minimal loss to the environment. PSC and PSD are agroenvironmental
indicators
used
to
estimate
P
availability
and
P
loss
to
the
environment.
However,
PSC
and PSD of agricultural soils had been never studied in Tanzanian soils. This study was
conducted to assess and estimate P availability, PSC and PSD and the risks of P losses in tropical
soils from Usangu basin popular for paddy farming. In total, 198 soil samples from 10 paddy
irrigation schemes were collected (November–December 2019) and analyzed for inherent P
(PM3), metal oxides of Aluminium (Al M3), iron (Fe M3), and calcium (Ca M3) as main PSC and
PSD determinant. The determined concentrations were in range of; P M3 014.9–974.69 mg/kg, Al
M3 234.56–3789.36 mg/kg, Fe M3 456.78–2980.23 mg/kg, and Ca M3 234.67–973.34 mg/kg.
Estimated PSCM3 ranged 5.62–34.85 mmol/kg with a mean value of 14.14 mmol/kg
corresponding to high status, ensuring high P holding capacity for plant uptake. However, some
soils had very low PSCM3 creating a risk of P loss to environment. Among soils, the estimated
PSD M3 ranged from 0.01 to 17.57% and was below (<24%), indicating low P loss risks to surface
and groundwater, however, some soils were observed to have PSDM3 above 15% which
correspond to a critical degree of phosphate saturation of 25% in a watershed using oxalate
extraction method. Therefore some sites were associated with high P loss to the environment,
immediate and precautionary actions for sustainable P management to increase productivity,
environmental safety and sustainability are needed to be in place
Main complementary food ingredients contributing to aflatoxin exposure to infants and young children in Kongwa, Tanzania
Get PDFThis research article published by MDPI, 2021Complementary foods (CFs) provided to infants and young children (IYC) in sub-Saharan Africa
contain ingredients that are susceptible to aflatoxin contamination. Chronic dietary exposure to
aflatoxins is associated with health consequences. This study assessed the risk of exposure of IYC
(6-12-month-old) in Kongwa, Tanzania to aflatoxins through CFs. The intake of aflatoxin
susceptible flours (ingredients) in CFs by 35 IYC was estimated through multiple-pass 24-hrdietary recalls. Samples of the ingredients were tested for aflatoxins using High-PerformanceLiquid Chromatography. Exposure of a child to aflatoxins was estimated by a deterministic
approach. The contribution of an ingredient to the overall exposure was estimated statistically. The
key ingredients of CFs consumed by the IYC were maize, sorghum, pearl millet, rice, and
groundnuts (pre-or post-blended with the other ingredients). Cereal and groundnut-based CFs weregiven as thin or stiff porridge. The average per capita daily intake of CFs was 89.45 g. About
82.14% of the CF ingredients were contaminated with aflatoxin B1 (AFB1) in the range of 0.27–
317 μg/kg, with a median of 3.96 μg/kg. AFB1 exposures ranged from 0.33 to 1168 ng/kg bw/day(median of 23.06 ng/kg bw/day). The Margins of Exposure were less than 10,000 for all the IYC,
signifying a public health concern. Post-blended groundnut flour, followed by maize, contributed
the most to the exposure of IYC to AFB1. Groundnut and maize used as CFs in Kongwa are likelyto be the main contributors to the exposure of IYC to AFB1. Caregivers should be advised to
replace maize and groundnuts with well-processed less susceptible cereals like pearl millet and
other legumes, respectively
High energy density materials based on fluorinated bridged trinitromethyl azo triazole derivatives: a quantum chemical study of thermodynamic and energetic properties
Get PDFA Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of
Master’s in Materials Science and Engineering of the Nelson Mandela African
Institution of Science and TechnologyHigh energy density materials (HEDM) have gained extensive attention due to their energetic
properties and safety issues. Nitro and fluoro groups, among others, have become viable
substituents in the HEDM triazole framework because of their particular contribution to
detonation properties and moderate sensitivity. In this study, fluorinated bis(trinitromethyl)
azo triazoles were designed theoretically using the Density Function Theory (DFT) approach
with hybrid functional B3LYP. The molecular structures, thermodynamic properties of
gaseous species (e.g., enthalpies of detonation and enthalpies of formation) and energetic
properties of solid materials (detonation heat Q, pressure PD and velocity VD) have been
investigated. The best characteristics attained for the designed azo fluorinated solid
compounds are as follows: Q 1650 – 1690 cal g
–1
, PD 44 – 46 GPa and VD 9.8 km s
–1
. These
characteristics are superior to those of conventional explosives, indicating that fluorinated
bis(trinitromethyl) azo triazoles are promising HEDM
The Effects of Cultivating Tobacco and Supplying Nitrogenous Fertilizers on Micronutrients Extractability in Loamy Sand and Sandy Soils
Get PDFThis research article published by MDPI, 2021This research was conducted to evaluate the trends of the extractable micronutrients boron
(B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) in soils differing in textures and collected
before tobacco cultivation, and in after unfertilized and fertilized (N10P18K24 and CAN 27%) plots.
The soils and tobacco leaves were assessed on the contents of the micronutrients after unfertilized and
fertilized tobacco cultivation. In soils, tobacco cultivation with fertilization increased the extractable
Cu, Fe, Mn, and Zn by 0.10, 11.03, 8.86, and 0.08 mg kg−1
, respectively, but decreased the extractable B
by 0.04 mg kg−1
. The effects of fertilization increased the extractable Cu, Fe, Mn, and Zn by 0.14, 14.29,
9.83, and 0.24 mg kg−1
, respectively, but decreased B by 0.08 mg kg−1
. The combination effects of
tobacco cultivation and fertilization increased the extractable Cu, Fe, Mn, and Zn by 0.24, 25.32, 18.69,
and 0.32 mg kg−1
, respectively, but decreased the extractable B by 0.12 mg kg−1
. The results revealed
that the solubility of the extractable Zn, Mn, Cu, and Fe in soils were increased by both tobacco
and fertilization, but the extractable B was decreased. The fertilization of the studied soils with
NPK + CAN fertilizers significantly increased the concentration of the extractable micronutrients in
tobacco leaves. Based on the findings of this study, further research must be conducted to investigate
the effects of tobacco cultivation on soil health and fertility beyond considering only soil pH, SOC,
micronutrients, and macronutrients. These studies should include the relationship between soil
fertility (pH, texture, CEC, base saturation, etc.), micronutrients, and agronomic practices on the
effect of tobacco cultivation on the extractability of B, Cu, Fe, Mn, and Zn
Application of modified lignocellulosic materials as green flocculants for brewery wastewater treatment
Get PDFA Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of
Master’s in Environmental Science and Engineering of the Nelson Mandela African
Institution of Science and TechnologyCoagulation–flocculation technique is usually used in wastewater treatment by employing
conventional inorganic materials such as alum and ferric chloride. Due to environmental
challenges associated with the use of inorganic flocculants, biopolymers are gaining ground as
alternative water treatment materials. In the present study, native cellulose and hemicelluloses
isolated from sugarcane bagasse were used in the removal of turbidity and biological oxygen
demand (BOD) from industrial wastewater. Isolated native cellulose was modified to
regenerated cellulose. Also, native cellulose, regenerated cellulose and hemicellulose were
carboxymethylated using sodium monochloroacetic acid. Functional groups on the isolated,
regenerated, and carboxymethylated biopolymers were examined using Fourier transform
infrared spectroscopy (FT-IR) and Carbon (C), Hydrogen (H), Nitrogen (N), Sulfur (S) and
Oxygen (O) (CHNS/O) analysis. The degree of substitution for regenerated and
carboxymethylated cellulosic materials were measured using recommended standard methods.
Carboxymethyl cellulose (CMC) with 1.3 degree of substitution reduced turbidity and BOD by
62.2 and 64%, respectively. Carboxymethyl regenerated-cellulose (CMC-II) at 1.1 degree of
substitution reduced turbidity and BOD by 55.6 and 60%, respectively. Carboxymethyl
hemicellulose (CMH) with 1.4 degree of substitution was capable of reducing turbidity and
BOD by 45.7 and 47%, respectively. Carboxymethylcellulose and hemicellulose have rarely
been used in the treatment of brewery wastewater. In the present study, these two novel
materials showed a good prospect for application in water and wastewater treatment
Heavy metals risk assessment of water and sediments collected from selected river tributaries of the Mara River in Tanzania
Get PDFThis research article published by Springer Nature, 2021This study investigated the levels of Pb, Hg, Cr, Cd, and As in water and sediments from the tributaries of the Mara River,
Tanzania. Pollution risk of water and sediments was investigated using seven indices and fve metals. During the dry
period, the highest concentration of Pb, Hg, Cr, Cd, and As in sediments was 17.45 ±1.22, 0.01, 1.56±0.5, 1.3±0.09, and
30.81±0.02 mg/kg, respectively. During the wet period, the highest concentration of Pb, Hg, Cr, Cd, and As in sediments
was 4.37±0.28, 0.012, 2.58±0.57, 2.25±0.35, and 53±0.02 mg/kg, respectively. For surface water, the respective highest concentrations of Pb, Hg, Cr, Cd, and As were 0.76±0.09, 0.04, 0.68±0.09, 0.74±0.1, and 0.47±0.06 mg/L for the
dry period. The wet period max concentrations for Pb, Hg, Cr, Cd, and As in surface water were 0.56, 0.03, 0.55±0.03,
0.48±0.03, and 0.4±0.03 mg/L, respectively. Principal component analysis results indicated dominant loadings for Pb
and As in sediments during the dry period. Comparison of sediment concentrations with sediment quality guidelines
revealed that As and Cd were enriched. Correlation coefcient results indicated that As had a strong negative correlation
with the rest of the elements in sediments during the dry period. In the wet period, As had a signifcant correlation with
Cd (r=0.92, p<0.01) in sediments. The analysis of environmental risks indicated signifcant enrichment of sediments
with As and Cd. It is important to put in place relevant control mechanisms targeting metals in the studied tributaries,
with a focus on As and Cd
Rainfall, fire and large-mammal-induced drivers of Vachellia drepanolobium establishment: Implications for woody plant encroachment in Maswa, Tanzania
Get PDFThis research article published by John Wiley & Sons, Inc., 2021Worldwide, open grass areas of savannah ecosystems are being transformed into shrubland. This woody plant encroachment is likely a result of factors such as rainfall, fire and secondary dispersal by ungulate herbivory. However, few experiments have been conducted to disentangle and quantify the role of these factors for seed germination in savannahs. We assessed in situ germination success of Vachellia drepanolobium seeds under simulated rainfall variability patterns, fire treatments and dung experiments in Maswa Game Reserve, Tanzania. Fire reduced seed germination by more than 13%, whereas germination in buffalo and elephant dung increased by 1% and 3% respectively. Additionally, intermediate simulated rainfall was more beneficial for seedling emergence success than large, infrequent simulated rainfall amounts, while shoot growth was twice as high under frequent and intermediate simulated rainfall treatments than under large infrequent simulated rainfall. Our results provide insights that bush fires, drought stress, and large rainfall events can suppress V. drepanolobium seedling emergence and growth. Hence, bush encroachment may be linked to management practices such as fire regimes and climatic conditions, i.e., frequent low rainfall conditions. Our results can help predict future patterns of encroachment under varying rainfall and fire events
Guanidinium tin halide perovskites: structural, electronic, and thermodynamic properties by quantum chemical study
Get PDFThis research article published by Springer Nature Switzerland AG., 2021The orthorhombic phase of guanidinium tin halide perovskites C(NH2)3SnX3, X = Cl, Br, I has been studied by quantum chemical method. The lattice parameters are optimized to obtain the minimum energy using the density functional theory with the generalized gradient approximation, GGA-PBE. The Kohn–Sham electronic band structures have been computed; the materials have direct bandgaps of 3.00, 2.47, and 1.78 eV for the C(NH2)3SnCl3, C(NH2)3SnBr3, and C(NH2)3SnI3, respectively, situated at the gamma symmetry points. The projected densities of states are analyzed and the contribution of the p- and s-states of the tin and halogen atoms evaluated. For the GUASnX3 compounds, thermodynamic stability to different decomposition routes has been assessed and standard enthalpies of formation obtained