http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/11009 2026-04-28T11:58:53Z http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/11041 Mathematical Modelling of the Spread of COVID-19 Cases in Sri Lanka Silva, K.K.T.S.; Dharmawardane, P.M.N. Sri Lanka confronted a substantial challenge in responding to the spread of the novel strain of coronavirus (SARS-CoV-2), which was declared as a pandemic by the World Health Organization. The government introduced multiple measures to contain the transmission of the virus within the country. This research provided information on COVID-19 and estimated the spread of the virus in Sri Lanka based on confirmed data from the national epidemiological reports for the period from October 01, 2020 to April 10, 2021. Stochastic modelling approaches were used to model the spread of the virus and its significance was also checked. The logistic growth model, where the number of infected cases are stochastic and the Susceptible-Infected-Recovered (SIR) model where the number of individuals who get disease, the number of deaths due to Coronavirus, and the number of recovered are stochastic, were employed under certain assumptions to identify the behavior of the spread of virus in a theoretical approach, during the second wave. The SIR model with a hyperparameter was used to improve the model fitting to actual data. Further, different infection and recovery rates were obtained using different time-variant scenarios. Results showed that the estimated cumulative cases were equal to 96845 within a certain period. It was also shown that both infection and recovery rates changed with time and followed different patterns. Due to changes in the COVID – 19 variants, the infected individuals also demonstrated different behaviors with increasing infection rate. 2021-01-01T00:00:00Z http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/11039 Brine shrimp lethality assay with selected medicinal plants extracts Suneka, S.; Manoranjan, T. Brine Shrimp Lethality Assay (BSLA) is a preliminary and important screening tool for cytotoxicity. This assay monitors toxic substances in plant extract and other based solvents. The toxic substance kills laboratory cultured larvae (nauplii). Artemia salina (nauplii), the first larval stage of many crustaceans, having an unsegmented body and a single eye. It is about 22 mm long. Organic extracts of the three terrestrial medicinal plants were investigated for the biological activity against BSLA with the help of Artemia salina. Those selected plant extracts were also tested for phytochemical analysis. The goal of the study is to evaluate the cytotoxicity of each plant extract and compare the activity among them by using BSLA test data. For the analysis, dried plant leaves and aerial parts were grounded into fine powder. About 500 grams of powder was extracted by cyclohexane, dichloromethane (DCM) and methanol respectively. The extract were filtered and concentrated in rotatory evaporator and each crude weight were recorded. According to the BSLA test of these plant extracts, the DCM extracts of Tephrosia purpurea (Sarphonka (E), Kavila (T)), Andrographis paniculata (Kings of bitter (E), Nilavembu (T)) and Oldenlandia umbellata (Chay root (E), Chaaya ver (T)) showed high activity than other solvents extracts. The LC50 (fifty percentage lethality concentration) value of dichloromethane extracts of T. purpurea was shown high value as 104.712 ppm, while A. paniculata and O. umbellate were shown 125.89 ppm and 223.872 ppm respectively. This result indicates the variety of active compound/s responsible for activity in the extracts especially in the DCM extracts. 2021-01-01T00:00:00Z http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/11036 Diversity and Abundance of Macroinvertebrates in Kaakkaithivu coastal waters, Jaffna estuary Vithusha, A.; Piratheepa, S. This study analyzed the diversity and abundance of aquatic macroinvertebrate community in the Kaakkaithivu coastal waters, Jaffna estuary. The sampling was carried out from July 2018 to January 2019. A total of 459 individuals of 15 macroinvertebrate families belonging to 20 taxa were identified based on their morphological characteristics by using standard keys. They are Coelenterates, Molluscs and Arthropods. According to the Shannon Weiner (H) and Simpson (D) indices, the highest species diversity value and abundance were found at the site-3 (H-2.7163, D-0.0836 and abundance-222) followed by site-2 (H-2.0511, D-0.1688 and abundance-143) and site-1 (H-1.2978, D-0.5822 and abundance- 94). Terebralia palustris (21.35%) and Cerithidea cingulata (20.05%) were the most abundance species belonging to the family Potamididae whereas the least abundant species were Cypraea sp and Metopograpsus sp (0.65% each) at Kaakkaithivu coastal waters. 2021-01-01T00:00:00Z http://repo.lib.jfn.ac.lk/ujrr/handle/123456789/11035 The effects of acid and cellulose concentrations on the acid hydrolysis efficiency of waste cellulose from Palmyrah fruit husk Srithevi, S.; Sashikesh, G. Underutilized cellulose from the Palmyrah Fruit Husk (PFH) was the source of the environmental problems. However, converting waste cellulose into glucose through acid hydrolysis to produce value-added fuels and chemicals has the potential to be both cost-effective and environmentally sustainable. The objective of this research study is to extract the cellulose from waste PFH and convert it to glucose monosaccharide using acid hydrolysis processes. Cellulose was extracted from the PFH using 1.5 % (w/v) of NaOH and 0.5 % (w/v) of Na2S solutions and it was identified using the Schultz reagent test. In the presence of DNS reagent, the yield percentage of glucose from the acid hydrolysis processes was measured using the Jasco V −570 UV-VIS-NIR spectrophotometer. The yield percentage of glucose increased when both the acid concentration and the extracted PFH cellulose solution were increased to a certain level. Furthermore, the optimal conditions were found to be 7.0 mol L−1 concentration of H2SO4, 1.0 × 104 ppm of extracted cellulose solution and 4 hours of acid hydrolysis, yielding 59.36 % glucose monosaccharides. As a result, PFH can be used to produce glucose monosaccharide as a suitable feedstock. 2021-01-01T00:00:00Z