Browsing by Author "Darshana, D."

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    Finite Element Analysis of Inflation Tyre Simulation Using Simulia Abaqus.
    (Faculty of Computing and Technology, University of Kelaniya, Sri Lanka., 2017) Fernando, A.; Darshana, D.
    Finite Element Analyses (FEA) are conducted in tyre industry either for a safety verification or prediction of the characteristics of virtual tyres. In the design stage of a tyre, it is impossible to determine its manufacturing performance. Therefore, modeling of a virtual tyre plays a significant role when predicting the performance and the characteristics of the tyre. At the end of the virtual simulation if the results do not satisfy the customer requirements, the tyre parameters can be easily changed without manufacturing a prototype sample. This inflation simulation is conducted to determine the outer diameter and the section width of the tyre after pressurizing it under given loading conditions. To obtain the required characteristics of the tyre, the input parameters are adjusted accordingly. It leads to analyze several versions of this virtual tyre simulations. Here, three different versions of virtual tyres are individually analyzed and, the best fitting parameters are determined. The accuracy of the FEA method is estimated by comparing simulation results with that of the prototype dimensions. In the method, three versions of the virtual tyres and the prototype tyres are individually compared to verify the results. As per the estimation, FEA of virtual model simulation shows low dimensional variance (2.38%) compared to that of the actual prototype simulation. Therefore, the results confirm the high accuracy of FEA method in virtual tyre simulation and the importance of implementing it in local industries. It would certainly cause to save precious time, unnecessary cost while increasing the quality of the products.
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    Interactions between penicillin and aqueous extracts of Plectranthus amboinicus and Plectranthus zeylanicus against Staphylococcus aureus.
    (Faculty of Science, University of Kelaniya Sri Lanka, 2024) Hafsa, M. F. F.; Darshana, D.; Wickramasinghe, S. S.; Tennakoon, S. H.; Napagoda, M. T.
    Penicillin, the pioneering antibiotic, has declined in effectiveness against Staphylococcus aureus due to increasing resistance, highlighting the urgent need for alternative strategies. Combining penicillin with medicinal plant extracts, such as Plectranthus amboinicus (Kapparawalliya) and Plectranthus zeylanicus (Iriveriya), rich in antibacterial compounds, offers a promising approach to revitalising its therapeutic efficacy. This study aimed to evaluate the potential interactions between penicillin and the aqueous extracts from P. amboinicus (PA) and P. zeylanicus (PZ) against both Methicillin-sensitive S. aureus (MSSA) and Methicillin-resistant S. aureus (MRSA). Whole plants of PA and PZ were macerated in distilled water for 24 hours at room temperature to prepare aqueous extracts. In the preliminary screening, the antibacterial activity of the aqueous extracts (500 mg/mL), and penicillin (3 mg/mL) were evaluated individually using the well-diffusion method. Ciprofloxacin (2 mg/mL) and distilled water were used as positive and negative controls, respectively. Subsequently, the minimum inhibitory concentration (MIC) of penicillin against MSSA and MRSA was determined using the broth microdilution method, followed by subculturing to determine minimum bactericidal concentrations (MBC). Aqueous extracts of PA and PZ were combined with different penicillin concentrations (2×MIC, MIC, 1/2×MIC, 1/4×MIC). The antibacterial activity of these combinations against MSSA and MRSA was evaluated using the well-diffusion method (well-diameter = 6 mm), measuring the inhibition zone diameter (IZD). The IZD of MIC of penicillin was compared with the IZD of penicillinPA and penicillin-PZ combinations to determine the interactions. Results showed that the aqueous extracts of PA and PZ did not demonstrate inhibition zones against MSSA and MRSA. The MIC and MBC of penicillin against MSSA were determined as 0.052 µg/mL and 100 µg/mL, respectively. However, the MIC of penicillin against MRSA was indeterminable, with an MBC exceeding 100 µg/mL. Notably, most combinations of penicillin with PA and PZ exhibited significantly higher IZD compared to MIC of penicillin alone (no inhibition zones), against both MSSA and MRSA (p < 0.05). Among all the combinations, the highest IZD was observed with the MIC+PZ combination against both MSSA and MRSA (IZD = 12.78 mm and 11.89 mm respectively). Potentiation was observed for the penicillin-PA combination, at penicillin concentration corresponding to the MIC against MSSA and at MIC, 1/2×MIC, 1/4×MIC against MRSA. With PZ, potentiation against MSSA and MRSA occurred at a penicillin concentration equivalent to the MIC. Additionally, penicillin combined with PZ demonstrated significantly stronger potentiation (p < 0.05) compared to penicillin-PA combinations, at equal penicillin concentrations, against both strains. In conclusion, the aqueous extracts from PA and PZ potentiated the antibacterial effectiveness of penicillin against MSSA and MRSA. This underscores the promise of these combinations for potent antibacterial therapies, suggesting a potential avenue for repurposing and reintroducing penicillin in combination with plant extracts to address antibiotic resistance. Further research should focus on understanding the mechanisms that enhance the effectiveness of penicillin when combined with PA and PZ.