Browsing by Author "Bahati, David"

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    Densification behaviour and structural properties of niobium and lanthanum-doped lead zirconate titanate and lead barium zirconate ferroelectrics for low-donor dopants concentrations
    (College of Natural and Applied Sciences, University of Dar es Salaam, 2019) Bahati, David; Makundi, Ismael
    In this paper we report the densification behaviour and structural properties of niobium and lanthanum-doped lead zirconate titanate (PZT) and lead barium zirconate (PBZ) ferroelectrics for low additive concentrations (0-2%). The PZT materials were calcined at 800 oC and sintered at 1200 oC while the PBZ materials were calcined at 850 oC and sintered at 1250 oC. Densification behaviour revealed that materials with lanthanum or niobium additives of greater than 0.5% for PZT and 0.2% for PBZ achieved complete densification. A strong distortion was observed in lattice parameters for lower dopants in which PBZ doped materials showed higher lattice distortions than PZT doped materials. The grain sizes decreased with increasing dopants concentrations for PZT while it increased with increasing dopants concentrations for PBZ materials.
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    Preparation and characterization of poly (lactic acid)-chitosan blend fibrous electrospun membrane loaded with bioactive glass nanoparticles for guided bone/tissue regeneration
    (Elsevier BV, 2024) Bahati, David; Bricha, Meriame; Semlali, Abdelhabib; El Mabrouk, Khalil
    In this study, bioactive fibrous membranes composed of poly (lactic) acid (PLA), chitosan (CHS), and strontium-doped bioactive glass nanoparticles (BG) were produced via electrospinning technique using a triple solvent system and characterized via thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), static contact angle (CA), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). All fiber samples exhibited consistent one-step thermal degradation profiles, regardless of BG content, and the intended BG contents in the membranes ware confirmed. The addition of 3% w/w CHS to form PLA-CHS blend lowered the glass transition temperature (Tg) by 1.62 °C. FTIR analysis validated the presence of CHS in the PLA-CHS blend fibers through the appearance of a low-intensity broad peak around 1658–1566 cm⁻1, indicating primary amide functional groups. Incorporating 3% w/w CHS reduced water contact angle by 7% and decreased fiber diameter by 57%. Wettability improved with increasing BG content, as confirmed by SEM images showing well-dispersed BG nanoparticles within the fibers. After 35 days of immersion in simulated body fluid (SBF), a substantial layer of hydroxyapatite (HA) with a Ca/P ratio resembling that of natural human bones coated the BG particles and fibers. The membranes demonstrated excellent cell adhesion capabilities, especially in the PLA_3%CHS and PLA_3% CHS_5% BG configurations, with minimal cellular toxicity compared to a well-known cell-killing agent, highlighting their biocompatibility. Incorporating chitosan and strontium-doped bioactive glass nanoparticles into PLA blends positively influenced cell viability and proliferation, emphasizing the enhanced cellular response resulting from surface modifications. These properties make these fibrous membranes promising for guided bone and tissue regeneration applications.
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    Teachers’ workload and class size as correlate of students’ academic performance in selected secondary schools in Singida urban
    (International Journal of Scientific Research and Management (IJSRM), 2020) Tarimo, Valentine Mathias; Bahati, David; Labito, Ramadhani Abedi
    The study sought to establish the relationship between teachers’ workload, class size and students’ academic performance from five selected secondary schools in Singida Urban. The study was guided by three objectives and three research hypotheses. The study employed correlational cross-sectional design. A sample size of two hundred ninety four respondents was randomly chosen from five secondary schools. A self-administered questionnaire was used to collect information from respondents. The collected data were analysed by Statistical Package for Social Scientists (SPSS) using Karl Pearson’s Linear Correlation Coefficient and Multiple Regression Analysis to assess the correlation between teachers’ workload and class size and students’ academic performance. The study results indicated that, there was no significant relationship between teachers’ workload and students’ academic performance in surveying secondary schools in Singida Urban at the five percent level of significance. Further, the findings show that class size was positively correlated with students’academic performance in secondary schools in Singida Urban. Also, there is a significant difference between teachers’ work load and class size in relation to students of academic performance in selected secondary schools in Singida Urban. Based on the study findings, it is recommended that, emphasis should be directed at improving class size if teachers and education stakeholders in Singida Urban have to increase students’ academic performance. The study concluded that, class size is found to be the best predictor of students’ academic performance in the surveyed secondary schools in Singida Urban