2647 research outputs found
Sort by
Strength and durability properties of concrete blended with pumice and scoria under combined attack of sulphate and chloride
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 TechnologyConcrete structures suffer serious deterioration under corrosive environment. Consequently,
the safety of these concrete structures is decreased. The influence of natural pumice (NP) and
natural scoria (NS) as supplementing cementing materials of concrete exposed to sulphate,
chloride and combined effect of sulphate and chloride is studied. Portland cement (PLC) was
replaced with NP or NS at a substitution level of 10%. Concrete samples were submerged in
portable water for 28 days. Afterwards, the specimens were immersed in 5% sodium sulphate
(Na2SO4), 5% sodium chloride (NaCl) and combined sodium sulphate and chloride solutions
for 28, 56 and 90 days. The results were compared between concrete mixes with NP or NS and
control mix (CT) with PLC. The effects of sulphate, chloride and combined sulphate and
chloride were evaluated in terms of change in weight, variation in compressive strength and
degree of damage. The compressive strength was not compromised at 10% substitution level.
It was observed that, concrete containing NP and NS have compressive strength of 46 MPa
(7.7%) and 44 MPa (3.04%) higher than 42.7 MPa of CT submerged in water for 90 days
respectively. Concrete samples immersed in 5% Na2SO4 solution, NP and NS has a
compressive strength around 45.5 MPa (15.4%) and 44.8 MPa (13.6%) higher than 39.4 MPa
of CT mix at 90 days, respectively. However, under 5% NaCl solution the compressive strength
of concrete containing NP and NS decreased up to 34.2 MPa (7.5%) and 32.5 MPa (7.2%) for
90 days cured samples. Moreover, under combined effect of 5% Na2SO4 and 5% NaCl concrete
containing NP and NS has a compressive strength around 29.8 MPa (8%) and 29.2 MPa (7.3%)
higher than 27.4 MPa of control mix at the exposure period of 90 days. It can be concluded that
NP and NS have extraordinary potential to be utilized as a cementitious material in concrete
Structural characterization of cassava linamarase-linamarin enzyme complex: an integrated computational approach
Get PDFThis research article was published by Taylor & Francis Group., 2021Cassava linamarase is a hydrolyzing enzyme that belongs to a glycoside hydrolase family 1 (GH1). It is responsible for breaking down linamarin to toxic cyanide. The enzyme provides a defensive mechanism for plants against herbivores and has various applications in many fields. Understanding the structure of linamarase at the molecular level is a key to avail its reaction mechanism. In this study, the three-dimensional (3D) structure of linamarase was built for the first time using homology modelling and used to study its interaction with linamarin. Molecular docking calculations established the binding and orientation nature of linamarin, while molecular dynamics (MD) simulation established protein-ligand complexes' stability. Binding-free energy based on MM/PBSA was further used to rescore the docking results. An ensemble structure was found to be relatively stable compared to the modelled structure. This study sheds light on the exploration of linamarase towards understanding its reaction mechanisms.
Communicated by Ramaswamy H. Sarm
Solvent effects on host-guest residence time and kinetics: further insights from metadynamics simulation of Toussaintine-A unbiding from chitosan nanoparticle
Get PDFThis research article published by Springer Nature Switzerland AG., 2021Solvents play an important role in host-guest intermolecular interactions. The kinetics and residence time of Toussaintine-A (TouA) unbinding from chitosan was investigated by means of well-tempered metadynamics and thermodynamic integration using two solvents, polar aprotic (DMSO), and polar protic (water). The kinetic rates were found to be strongly dependent on the solvent polarity; hence, the unbinding rate proceeded much faster in DMSO compared to water. DMSO tends to participate less in a chemical reaction by weakening the intermolecular interaction between chitosan and TouA due to lack of acidic hydrogen resulting in a reduction of the transition state. On the other hand, water, which ought to donate hydrogen atoms, sustains a strong interaction and hence large barrier heights. Consequently, this reduces the unbinding rate and increases the residence time. Binding free energy from thermodynamic integration suggests a thermodynamic stable chitosan-TouA complex in water than in DMSO
Sub- and Supercritical Water Gasification of Rice Husk: Parametric Optimization Using the I-Optimality Criterion.
Get PDFThis research article published by ACS Publications, 2021In this study, rice husk biomass was gasified under sub- and supercritical water conditions in an autoclave reactor. The effect of temperature (350-500 °C), residence time (30-120 min), and feed concentration (3-10 wt %) was experimentally studied using the response surface methodology in relation to the yield of gasification products. The quadratic models have been suggested for both responses. Based on the models, the quantitative relationship between various operational conditions and the responses will reliably forecast the experimental outcomes. The findings revealed that higher temperatures, longer residence times, and lower feed concentrations favored high gas yields. The lowest tar yield obtained was 2.98 wt %, while the highest gasification efficiency and gas volume attained were 64.27% and 423 mL/g, respectively. The ANOVA test showed that the order of the effects of the factors on all responses except gravimetric tar yield follows temperature > feed concentration > residence time. The gravimetric tar yield followed a different trend: temperature > residence time > feed concentration. The results revealed that SCW gasification could provide an effective mechanism for transforming the energy content of RH into a substantial fuel product
A Nutrition-Sensitive Agroecology Intervention in Rural Tanzania Increases Children's Dietary Diversity and Household Food Security But Does Not Change Child Anthropometry: Results from a Cluster-Randomized Trial.
Get PDFThis research article published by Oxford University Press, 2021Background
There are urgent calls for the transformation of agriculture and food systems to address human and planetary health issues. Nutrition-sensitive agriculture and agroecology promise interconnected solutions to these challenges, but evidence of their impact has been limited.
Objectives
In a cluster-randomized trial (NCT02761876), we examined whether a nutrition-sensitive agroecology intervention in rural Tanzania could improve children's dietary diversity. Secondary outcomes were food insecurity and child anthropometry. We also posited that such an intervention would improve sustainable agricultural practices (e.g., agrobiodiversity, intercropping), women's empowerment (e.g., participation in decision making, time use), and women's well-being (e.g., dietary diversity, depression).
Methods
Food-insecure smallholder farmers with children aged <1 y from 20 villages in Singida, Tanzania, were invited to participate. Villages were paired and publicly randomized; control villages received the intervention after 2 y. One man and 1 woman “mentor farmer” were elected from each intervention village to lead their peers in agroecological learning on topics including legume intensification, nutrition, and women's empowerment. Impact was estimated using longitudinal difference-in-differences fixed-effects regression analyses.
Results
A total of 591 households (intervention: n = 296; control: n = 295) were enrolled; 90.0% were retained to study end. After 2 growing seasons, the intervention improved children's dietary diversity score by 0.57 food groups (out of 7; P < 0.01), and the percentage of children achieving minimum dietary diversity (≥4 food groups) increased by 9.9 percentage points during the postharvest season. The intervention significantly reduced household food insecurity but had no significant impact on child anthropometry. The intervention also improved a range of sustainable agriculture, women's empowerment, and women's well-being outcomes.
Conclusions
The magnitude of the intervention's impacts was similar to or larger than that of other nutrition-sensitive interventions that provided more substantial inputs but were not agroecologically focused. These data suggest the untapped potential for nutrition-sensitive agroecological approaches to achieve human health while promoting sustainable agricultural practices
Trends towards Effective Analysis of Fluorinated Compounds Using Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
Get PDFThis research article published by Hindawi, 2021Increased demand for monitoring and identification of novel and unknown fluorinated compounds (FCs) has demonstrated the need of sensitive fluorine-specific detectors for unknown FCs in both biological and environmental matrices. Inductively coupled plasma mass spectrometry (ICP-MS) is a promising technique for analysis of FCs and has been rated as the most powerful tool in analytical chemistry. However, direct determination of fluorine using this technique is challenged by high ionization potential of fluorine together with spectral and nonspectral interferences which affect the quality of results. To enhance the quality of results, several studies have reported modifications of a conventional ICP-MS analysis procedure on sample preparation, introduction, analysis, and instrument optimization. Therefore, the focus of this study is to discuss different ICP-MS optimizations and future trends towards the effective analysis of FCs using ICP-MS
Detection of Rift Valley Fever Virus Interepidemic Activity in Lower Moshi area of Kilimanjaro Region, North Eastern Tanzania: A Community Survey
Get PDFThis research article published by Research square, 2021Background: Rift Valley fever virus (RVFV) is a zoonotic arbovirus of public health impact infecting livestock, wildlife, and humans mainly in Africa and other parts of the world. Despite its public health importance, mechanisms of RVFV maintenance during inter-epidemic (IEPS) periods and potentially spread to new areas remain unclear.We aimed to comparatively examine exposure to RVFV and RVFV infection among humans, goats and mosquitoes in an agro-pastoral community in Lower Moshi area of Moshi rural district.
Results:Results show that the male gender was related to RVFV seropositivity (χ2 = 5.351; p=0.030). Being 50 years and above was related to seropositivity (χ2=14.430; p=0.006) whereas bed net use, larger numbers of persons living in the same house (>7 persons) and RVFV seropositivity in goats were related to higher seropositivity to RVFV among humans (χ2=6.003; p=0.021, χ2=23.213; p=0.000 and 27.053; p=0.000), respectively.RVFV antibody concentrations were only marginally higher in humans without statistically significant difference [t (112) =0.526; p=0.60)]. By the use of RT-qPCR, goats exhibited the highest RVFV infection rate of 4.1%, followed by humans (2.6%), Aedes spp(2.3%), and Culex spp(1.5%).
Conclusions: In the absence of RVFV infection data in areas nearby the study site, our findings suggest Lower Moshi area as a potential hotspot for RVF, posing the danger of being a source of RVFV spread to other areas. Goats had the highest infection rate, suggesting goats as important hosts in the virus maintenance during IEPs. We recommend the design and implementation of strategies that will warrant effective active surveillance of RVF through the identification of RVF hotspots for targeted control of RVF
Impact of climate change on groundwater recharge in the lake Manyara catchment, Tanzania
Get PDFThis research article is published in scientific Africa volume 15Groundwater account for about 60 to 80% of water supply to the population of Tanzania's semi-arid regions for domestic and agriculture uses. Despite the importance of groundwater resource in semi-arid areas, limited information exists on the recharge amount and potential recharge zones in Tanzania in the context of climate change which could result in unsustainable withdrawals. This study aimed to estimate the potential impact of climate change on groundwater recharge and identify potential recharge zones in the Lake Manyara catchment using Water and Energy Transfer between Soil, Plants and Atmosphere under the quasi-steady State (WetSpass) model. The WetSpass model was setup and calibrated using hydro-meteorological data (rainfall, temperature, wind speed, potential evapotranspiration, and groundwater depth) and biophysical data (soil, land use, topography, and slope). Simulated rainfall, temperature and potential evapotranspiration from an ensemble of four CORDEX-Africa regional climate models for the period 2021–2050 under the Representative Concentration Pathway (RCP 8.5) scenario (hereafter referred as business-as-usual scenario) were used as input in the WetSpass model for the climate change impact assessment. WetSpass model calibration using the water balance equation showed a coefficient of determination (R2) value of 0.9 and Root-Mean-Square Error (RMSE) of 0.49 mm/yr between the simulated and calculated recharge. It was determined that the mean annual recharge of 53.9 mm/year (149 MCM/year) for the period 1989–2018 would increase by 7.9% in the future (2021–2050) under the business-as-usual climate scenario, due to the increase in rainfall. Seasonality and spatial differences in recharge amount were observed, with recharge projected to increase in the dry season and at areas that receive high amount of rainfall. Potential recharge zones in the catchment were found mostly around the northern part near Ngorongoro, the south-western part, and around Mbulu region. Findings from this study would help policymakers, and local stakeholders in planning and management of the groundwater resources for sustainable development
Prevalence and risk factors associated with subclinical mastitis in lactating dairy cows under smallholder dairy farming in North East Tanzania
Get PDFThis research article was published by Journal of Veterinary Medicine and Animal Health Vol. 13, 2021A cross-sectional survey was carried out between October 2016 and May 2017 to determine the prevalence of subclinical mastitis (SCM), associated bacterial pathogens and risk factors under smallholdersmall holder dairy farms in North East Tanzania. The study involved 195 cross breed dairy cows from 130 dairy farms. Data were collected based on questionnaire interview, direct observation, screening using California Mastitis Test (CMT) and culture of bacteria. The overall prevalence of SCM based on California Mastitis Test (CMT) was 70.8 and 66.4% and bacteria isolation recorded at 56.4 and 38.4% at cow and quarter levels, respectively. Prevalence defined by CMT was significantly (p<0.0001) associated with wet-dirty bedding material (OR=11.61) and poor udder (OR =6.67). Increased culture-positivity at quarter level was significantly associated with CMT-positive cows (OR= 20.59), teat injuries (OR=23.56), wooden floor (OR=2.02) and poor udder hygiene (OR =2.16). Stripping method of hand milking and first and second parity were significantly associated with lower prevalence of CMT-positive cows and culture positive quarters (p<0.05). Major bacteria species isolated included Staphylococcus aureus (55.4%), Staphylococcus epidermidis (10.8%), Escherichia coli (7.9%) and Streptococcus agalactiae (5.9%). This study demonstrated SCM is a major health constraint of dairy cattle in North Eastern Tanzania
Balancing Bees and Livestock: Pastoralist Knowledge, Perceptions and Implications for Pollinator Conservation in Rangelands, Northern Tanzania
Get PDFThis research article published by SAGE journal, 2021Insect pollinators provide numerous ecosystem services that support other living organisms. While pollinators play a large
role in cropping systems, little is known about their presence and function in rangeland ecosystems, which have recently
become fragmented and overexploited at an extraordinary rate. We assessed local Maasai knowledge on insect pollinators
and how pollinators affect livelihood diversification in Simanjiro rangelands, Tanzania. Through questionnaires, key informant
interviews, focus group discussions, and field observations, we found varied insect knowledge among Maasai herders.
Lasioglossum of sub genus Ipomalictus and Syriphidae were the least commonly recognized pollinators as only 24%, and 7%
of participants could identify them, respectively. Responses varied significantly between men and women (F ¼ 7.397,
p ¼.007). Commiphora africana, Acacia mellifera and Albizia anthelmintica were noted as most important bee forage plants
while observations showed Aspilia mossambicensis, Justicia debile and Acacia tortilis. Most (77%) of Maasai herders showed
limited ability to link pollinators and rangeland wellbeing. Beekeeping contributed to livelihood diversification for 61% of
respondents, with women participating more frequently than men (v2 ¼ 46.962, p ¼.0001). Beekeeping was positively
influenced by education level (R ¼ .421, p <.0001) and occupation (R ¼ .194, p ¼.009). Pollinator declines were attributed
to climate change (47%), agriculture (37%), and habitat destruction (8%). We conclude that Maasai have limited knowledge of
common pollinator groups and their roles. Community outreach and training should bridge the knowledge gap in pastoralist
communities to fully realize pollinator benefits and highlight the importance of rangeland health