Browsing by Author "Sahini, Mtabazi Geofrey"

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    A comparative in-vitro study on antimicrobial efficacy of on-market alcohol-based hand washing sanitizers towards combating microbes and its application in combating Covid-19 global outbreak
    (Elsevier, 2022) Vuai, Said Ali Hamad; Sahini, Mtabazi Geofrey; Sule, Khalfani Salim; Ripanda, Asha Shabani; Mwanga, Hossein Miraji
    The coronavirus disease 2019 (COVID-19) outbreak has created endless social, economic, and political fear in the global human population. Measures employed include frequent washing hands and using alcohol-based hand sanitisers and hand rubs as instant hand hygiene products. Due to the need to mitigate the pandermic, there is an increase in the local production of alcohol-based hand sanitisers, whose quality and efficacy against germs and the virus are questionable. Therefore, the current study investigated the in-vitro antimicrobial efficacy of on-market alcohol-based handwashing sanitizers used to mitigate the Covid-19 global outbreak toward combating enveloped bacteria such as E. Coli, P. aeroginosa, S. aureus, and a fungus C. albicans. The antimicrobial effectiveness ofalcohol-based hand sanitizer was performed by the agar well diffusion method, and the analysis of variance (ANOVA) model was used for statistical analysis. Results indicate that alcohol hand-based sanitizers were more effective in inhibiting P. aeroginosa, with a mean zone of inhibition of 12.47 mm, followed by E. coli, a gramnegative bacterium with a mean zone of inhibition of 12.13 mm than both S. aureus and C. albicans as grampositive bacteria, and fungi respectively had the same inhibition average of 11.40 mm. The overall mean diameter of inhibition was statistically significantly different among the fifteen tested products. Only one brand of alcohol-based hand sanitizers was the most effective in inhibiting microbes. Less effective sanitizers may impair Covid 19 mitigation efforts and put the population at risk instead of protecting it. Indicating the need for all materials used to mitigate Covid 19 pandermic, including alcohol-based hand sanitizers, to be evaluated and monitored to ensure public health safety
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    A comparative in-vitro study on antimicrobial efficacy of on-market alcohol-based hand washing sanitizers towards combating microbes and its application in combating Covid-19 global outbreak
    (Elsevier, 2022) Vuai, Said Ali Hamad; Sahini, Mtabazi Geofrey; Sule, Khalfani Salim; Ripanda, Asha Shabani; Mwanga, Hossein Miraji
    The coronavirus disease 2019 (COVID-19) outbreak has created endless social, economic, and political fear in the global human population. Measures employed include frequent washing hands and using alcohol-based hand sanitisers and hand rubs as instant hand hygiene products. Due to the need to mitigate the pandermic, there is an increase in the local production of alcohol-based hand sanitisers, whose quality and efficacy against germs and the virus are questionable. Therefore, the current study investigated the in-vitro antimicrobial efficacy of on-market alcohol-based handwashing sanitizers used to mitigate the Covid-19 global outbreak toward combating enveloped bacteria such as E. Coli, P. aeroginosa, S. aureus, and a fungus C. albicans. The antimicrobial effectiveness of alcohol-based hand sanitizer was performed by the agar well diffusion method, and the analysis of variance (ANOVA) model was used for statistical analysis. Results indicate that alcohol hand-based sanitizers were more effective in inhibiting P. aeroginosa, with a mean zone of inhibition of 12.47 mm, followed by E. coli, a gramnegative bacterium with a mean zone of inhibition of 12.13 mm than both S. aureus and C. albicans as grampositive bacteria, and fungi respectively had the same inhibition average of 11.40 mm. The overall mean diameter of inhibition was statistically significantly different among the fifteen tested products. Only one brand of alcohol-based hand sanitizers was the most effective in inhibiting microbes. Less effective sanitizers may impair Covid 19 mitigation efforts and put the population at risk instead of protecting it. Indicating the need for all materials used to mitigate Covid 19 pandermic, including alcohol-based hand sanitizers, to be evaluated and monitored to ensure public health safety.
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    Ferroelectric relaxor behaviour in Bi and K/Na-substituted solid solutions of tetragonal tungsten bronze PbNb2O6
    (Elsevier BV, 2024) Sahini, Mtabazi Geofrey; Mwankemwa, Benard Samwel; Elisadiki, Joyce
    Lead metaniobate (PbNb2O6 or PNO) belongs to the tetragonal tungsten bronze (TTB) family. There are three polymorphic forms of PNO: tetragonal (stable at high temperature), rhombohedral (stable at room temperature), and the metastable orthorhombic phase, which has ferroelectric properties. The metastable orthorhombic phase is formed by quenching from the high temperature tetragonal phase due to the reconstructive/sluggish tetragonal to rhombohedral phase transition. A suitable ionic substitution can also lead to the stable ferroelectric orthorhombic phase. Stabilization of the ferroelectric orthorhombic phase by ionic substitution, and the formation of ferroelectric relaxors with increased amounts of dopants is hereby reported for the compositions Pb(1-x)Bi(x/2K(x/2)Nb2O6 and Pb(1-x)Bi(x/2)Na(x/2)Nb2O6. The solid solutions of PNO showed evidence of linked dielectric relaxation and ferroelectricity, validating the distinctive ferroelectric relaxor behaviour for the compositions Pb0.6Bi0.2K0.2Nb2O6 and Pb0.6Bi0.2Na0.2Nb2O6. As the concentrations of bismuth (Bi) and potassium/sodium (K/Na) dopants increased, the Curie temperature (Tc), or the temperature corresponding to the maximum dielectric permittivity (Tm), dropped. By using the Uchino-Nomura relation as a modification of the Curie-Weiss law, it was established that the Pb0.6Bi0.2K0.2Nb2O6 solid solution exhibit higher degree of diffuseness than Pb0.6Bi0.2Na0.2Nb2O6 at the transitions. The width of the ferroelectric hysteresis loop increased as the percentage of dopants increased, from x = 0.1 to x = 0.3. At x = 0.4, a narrow ferroelectric hysteresis loop and a frequency-dependent Tm abruptly formed, which is indicative of a ferroelectric relaxor.
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    Mechanism of hydrothermal growth of ferroelectric PZT nanowires
    (Elsevier, 2012) Wang, Jin; Durussel, Alexandre; Sandu, Cosmin Silviu; Sahini, Mtabazi Geofrey; He, Zhangbing; Setter, Nava
    The formation mechanism of hydrothermally grown monocrystalline ferroelectric PZT nanowires is investigated. It is shown that the growth proceeds via a two-step process. Particles of the centrosymmetric PX-phase grow initially, having a fibrous morphology which is compatible with the highly anisotropic crystalline structure of this material. In the second stage, the PX-phase transforms into the ferroelectric perovskite phase, retaining the initial fibrous morphology. The solubility limit of Zr ions in the PX phase is maintained into the perovskite phase. While the PX and the perovskite phases have a similar composition, the reconstructive transformation process, in which edge-sharing octahedra chains of the PX-phase transform into a 3D network of corner sharing octahedra in the perovskite, involves incorporation and then release of oxygen (or hydroxyl).
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    Perspective and control of cation interdiffusion and interface reactions in solid oxide fuel cells (SOFCs)
    (Elsevier, 2023) Sahini, Mtabazi Geofrey; Lupyana, Samwel Daud
    The occurrence of cation interdiffusion during sintering and operation of Solid Oxide Fuel Cells (SOFCs) is inevitable, due to high temperatures and chemical potential gradients. Cation interdiffusion may be followed by solid state reaction, resulting into the formation of secondary phases. Understanding of the factors that trigger the occurrence of cation interdiffusion and interface reactions is crucial towards controlling their occurrences. Here, we have discussed the phenomena associated with cation interdiffusion in solid oxide fuel cells. We have established that cation interdiffusion and interface reactions occur both during the high temperature sintering and during SOFC operations. Case examples where cation interdiffusion and subsequent interface reactions form secondary phases are discussed. The various methods that can be used to minimize or control the occurrence of cation interdiffusion are discussed: the use of diffusion barriers, fabrication of strontium free cathode materials, lowering the sintering temperature and the SOFC operating temperature
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    Use of phyto-based polymeric material as chemical admixture in well cement slurry formulation
    (Elsevier, 2021) Lupyana, Samwel Daud; Sahini, Mtabazi Geofrey; Kattiba, Saada Msafiri; Gu, Jun
    Plants extracts contain a wide range of organic components and have been used as admixtures in modifying different cement properties. In this study, aqueous extract of Euphorbia Tirucalli (ET) as bio-admixture was characterized and tested for potential use in the preparation of well cement slurry. Several tests such as setting time tests, fluid loss tests, rheological properties of well cement slurries incorporating different proportions of the ET and the reference slurries without ET were conducted and evaluated. Phytochemical composition of ET was investigated by using Gas Chromatography-Mass Spectrometer (GCMS) analytical technique. Interactions between the bio-admixture and cement components during hydration were also characterized by Fourier Transform-Infrared (FT-IR) spectroscopic technique. GC–MS analysis indicates the presence of the palmitic acid groups such as hexadecanoic acid, methyl ester, n-Hexadecanoic acid and 9-Hexadecanoilc acid and the fatty acid components commonly known as linoleic acid. Incorporation of the bio-admixture shows to enhance fluid loss properties and slurry rheology. Also, the bio-admixture indicates promoting retardation of cement hydration due to increase in setting times with increase in mix proportions. These properties indicated to be dependent to the bio-admixture concentration. FT-IR spectroscopic investigations suggests possible interaction between bio-admixture and the ionic species in the cement slurry.