International Research Symposium on Pure and Applied Sciences (IRSPAS)
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Item A study on Dengue spread in Western province: using Spatial and Cluster analysis.(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Kethmi, G. A. P.; Premarathna, L. P. N. D.Dengue virus is transmitted to humans through the bite of infected Aedes mosquitoes, mostly Aedes aegypti. According to National dengue control unit of Sri Lanka, the recent outbreak of dengue fever in the country was reported on July 2017. Since the life cycle of a mosquito is short, it is highly influenced by the variations in the environment. Also, Sri Lanka has a changing weather over time, hence the spread of dengue mosquito is time dependant. Considering these facts objectives of the study were to identify the correlation between number of dengue incidences and the environmental factors such as temperature, rainfall and humidity, recognize homogeneous areas of dengue and discover dengue dense area and non-dense area in Western province. Agglomerative hierarchical clustering method used to observe homogenous areas in the study area. In this method, initially each observation is considered as a cluster and continue the procedure by connecting most similar observations. Several linkage methods that can be used to join observations into clusters. From literature, Ward’s method proposed as the best linkage method in clustering where total within-cluster variance calculated and at every step clusters with minimum between cluster variance connected. After constructing the cluster dendrogram by connecting appropriate clusters, the optimum number of clusters identified using Elbow method. Spatial analysis explains a behaviour or a pattern of a variable geographically. Geographical maps are used to find the dengue dense and dengue non-dense areas. Number of dengue incidences and environmental factors for the period 2013 to 2017 of three districts in Western province were used for this study. R statistical software used to conduct the analysis. A descriptive analysis was carried out and outliers were treated using Winsorizing method. Normality of each variable was examined. Pearson’s correlation coefficient calculated when variables are normally distributed otherwise; Spearman correlation coefficient calculated. According to the results obtained, rainfall and humidity have a negative correlation with number of dengue incidences while temperature has a positive correlation. Three clusters identified as follows; first two months and last three months fell into one cluster, March and April were the next and remaining months as another cluster. Cluster analysis showed that, during the first period of monsoon season of the year, there is an increase in the spread of dengue virus in the Western province. Spatial analysis showed that the Colombo as the dengue dense and Kalutara as the dengue non-dense area in the Western provinceItem A mathematical model to analyze the dynamics of Dengue transmission: A case study based on Western Province, Sri Lanka(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Gammune, D. H. V.; Premarathna, L. P. N. D.Dengue fever, which is a rapidly spreading mosquito-borne viral disease, has become a major public health problem in the world, including Sri Lanka. The Western Province of Sri Lanka has been experiencing a very high number of Dengue incidences throughout the past few decades. According to literature, considerations have not been paid on the dynamics of Dengue transmission and interplay of climate changes with mosquito biting rates. Therefore, a mathematical model is to be introduced to integrate the behavior of the climate changes as well as the mosquito biting rates with the dynamics of dengue transmission. Dengue is transmitted only through the bites of the infected mosquitoes, and the number of mosquito bites during a certain period is directly proportional with the number of Dengue cases reported during the same period. The aims of the research are, therefore, to identify the behavior of the climate factors on the dynamics of Dengue transmission, to develop a mathematical model to analyze the dynamics of spread of Dengue and to predict the future Dengue outbreaks of the Western province of Sri Lanka, using the developed model. Since the climate variables play a greater role in Dengue transmission, the correlation between the number of Dengue incidences and the climatic variables is analyzed. The vector-borne compartmental models have been used in the literature to understand the dynamics of different types of epidemic diseases. Hence, in this study, a similar approach is used to analyze the Dengue transmission, which considers the influences of climate changes on the Dengue transmission dynamics via the time-varying mosquito biting rate. A significant positive correlation is found between the reported number of Dengue incidences and the average temperature. According to the analysis, the developed model, together with the estimated mosquito biting rates, gives a statistically significant goodness of fit between the simulation results and the reported number of Dengue incidences. The analysis highlights that the dynamics of Dengue transmission are less sensitive to the variation in the mosquito population size than the changes in the mosquito-biting rate. The proposed model is validated by comparing the predictions with the data, which are not used in the model calibration. The model validation exhibits that there is a statistically significant fit between the model predictions and the actual data. The proposed vector-borne compartmental model along with the estimated mosquito biting rates, therefore, can be used to predict the dynamics of Dengue transmission with a high accuracyItem Bioactive properties of Rambutan (Nephelium lappaceum L.) and Durian (Durio zibethinus Murr.) peel extracts(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Silva, A.G.; Wickramaarachchi, S.; Attanayake, R. N.; Rajapakse, C. S. K.Although these fruits are seasonal, a considerable amount of Rambutan (Nephelium lappaceum L.) and Durian (Durio zibethinus Murr.) fruit residues (mainly peels) are collected each year as waste materials, due to the significant volume of trade of these fruits. Therefore, present work was initiated with the aim of evaluating the impact of these residues lying as waste and possible re-use, by investigating the bioactive properties in peels of rambutan and durian. Methanol extracts of Rambutan and Durian peels were sequentially extracted with hexane, chloroform and methanol. First, methanol extracts of peels were subjected to phytochemical screening following standard procedures and results revealed that rambutan and durian peels were rich in polyphenols, flavonoids, steroids, coumarin, etc. Total phenolic content (TPC) and total flavonoid content (TFC) of methanol extracts of peels were determined using Folin-Ciocalteu and aluminium chloride method, respectively. Results showed that TPC and TFC in methanol extract of durian peels were (11.39 ± 0.49 mg GAE/g dry weight, 257.20 ± 5.14 mg Catechin /g dry weight) higher than those of Rambutan peels (2.73 ± 0.15 mg GAE/g dry weight, 198.00 ± 1.89 mg Catechin /g dry weight). Further, the antioxidant activity of methanol extracts of peels and its fractions were investigated using 1, 1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging assay and the correlation with their TPC and TFC were examined using Pearson’s correlation analysis. The strongest antioxidant activity was observed in hexane fraction of Rambutan peels with IC50 value of 13.49 ± 0.52 μg/mL, and which was lower than that of the control, butylated hydroxytoluene (43.70 ± 0.89 μg/mL). Significant positive correlations were observed between TPC and TFC in fractions of rambutan and durian peels with their DPPH radical scavenging activity indicating that phenolics and flavonoids in rambutan and durian peels may contribute to their strong antioxidant activities. The antimicrobial activity of the extracts of peels and its fractions were assessed by using disc diffusion method against a bacterial species of Staphylococcus aureus and fungal species, Fusarium oxyporum and Aspergillus flavus. The lowest concentration of methanolic extract of durian and rambutan peels that showed an inhibition against Staphylococcus aureus was 31.25 μg/mL. It was also found out that neither peels of rambutan nor durian had antifungal activity against the two selected fungal species. Results revealed that the peels of rambutan and durian are potential sources of antioxidants and antibacterial agentsItem Study on effect of microfauna and some abiotic parameters for the prevalence of mosquito larvae inhabiting marshlands(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Menike, P.M.I.D.; Amarasinghe, L.D.This study was carried out in selected marshlands of Kelaniya in Sri Lanka to determine the prevalence of various mosquito species larvae and their association with biotic and abiotic parameters of the habitat. Larval sampling, recording of physico chemical parameters and microfauna identification were done at monthly interval from March 2015 to August 2015. The study was carried out in eight marshlands with varying Biochemical Oxygen Demand (BOD) levels and total number of 893 mosquito larvae were collected (n=144). Culex gelidus, Cx. whitmorei, Cx. tritaeniorhynchus, Cx. quinquefasciatus, Cx. fuscocephala and Anopheles sp. 1 were the species/taxa identified. Cx. gelidus, Cx. whitmorei, Cx. quinquefasciatus were found in mashes with BOD level ranging from 1.5-2 mg/L and Cx. fuscocephala with 1-1.5 mg/L. Anopheles sp. 1 was found in significantly low level. pH levels in these habitats did not vary significantly and lied between 6.5-7.0. When Cx. whitmorei and Cx. gelidus co-existed in one habitat, it was found a significant negative correlation between the populations of two species. Similar results were found when Cx. quinquefasciatus with Cx. gelidus present together in same habitat. However, Cx. fuscocephala and Cx. gelidus when present together in same habitat, it was shown a positive correlation. In marshlands, 14 genera of microfauna were identified (n=144). Among them Zoothamnium sp 1 was most common and found higher densities and followed by Difflugia sp 1, Nauplius larva, Cyclops sp 1, and Daphnia sp 1. Pearson correlation showed that there was a correlation between the density of mosquito larvae and associated microfauna. Zoothamnium sp. 1 was given negative correlation with the Cx. gelidus when they present in higher density. A significant positive correlation was obtained between Daphnia sp. 1, Difflugia sp. 1, Nauplius larva and Keratella sp. 1 with mosquito larvae. Hence, there is no relationship between microfauna and mosquito populations. However, this may depend on the BOD of the habitat.