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Fostering education for environmental sustainability: level of competencies on reducing environmental pollution of junior secondary students in Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2014-11-01) Liyanage, T. I. S. S.
Education for Environmental Sustainability (EES) aims to develop students' sensitivity, awareness, knowledge, attitudes, skills, and practices related to the environment and the sustainable use of its resources. It not only empowers students on environmental concerns but also connects them to more sustainable lifestyles, enabling them to become environmentally literate. This cross-sectional survey was conducted to assess the environmental literacy of junior secondary students (Grades 6 to 9) in selected Sri Lankan schools. The aim of the study was to determine students' competency levels in reducing environmental pollution. The sample included 442 students from three districts in the Western Province (Colombo, Gampaha, and Kalutara), selected using random stratified sampling techniques. A questionnaire with multiple-choice questions was used as the research instrument. Students' competency in organic farming, eco-friendly energy sources, reducing/recycling, and judgment on eco-friendly practices was assessed. Competency was measured by students' ability to identify and analyse environmental issues, ask relevant questions, evaluate and make personal judgments, and use evidence and knowledge to defend their positions. The findings revealed that students' competency levels in the focused areas improved with more effective EES implementations in school education. Students in the Colombo District recorded the highest competency level (μ = 0.55 ± 0.26), while the lowest was recorded in the Gampaha District (µ = 0.53 ± 0.26). Competency varied from 0 to 1 across all three districts. Grade 8 students showed the highest competency (μ = 0.55 ± 0.22), while Grade 6 students recorded the lowest (µ = 0.48 ± 0.28). A significant association was observed between the student category and organic farming (p < 0.05), as well as reducing/recycling and willingness to engage in pollution reduction activities (p < 0.05). There were significant variations across districts and among the three grades (p < 0.05). In conclusion, the findings underscore the critical role of EES in enhancing students' environmental literacy and greater awareness and promoting active participation in sustainable practices, paving the way for a more environmentally responsible generation.
Effective corrosion barrier of cinnamon leaf oil incorporated polypyrrole layers for mild steel
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Peradeniya, Sri Lanka, 2020-11-01) Palipana, P. W. G. K.; Revon, M. H. N.; Priyantha, N.
Mild steel, a type of steel commonly used in industry, is prone to corrosion under certain environmental conditions, which has limited its industrial applications, necessitating intensive study into corrosion prevention techniques. In recent years, conducting polymers and green corrosion inhibitors have been independently identified as corrosion inhibitors, and less consideration has been given over the past years on the combined effect of polymers and natural inhibitors. This study aimed to investigate the corrosion inhibition efficiency by cinnamon leaf oil embedded polypyrrole layers. The electrodeposition of polypyrrole on mild steel was employed using cyclic voltametric scans from -0.2 V to 1.0 V in oxalic acid medium and polymer-coated specimens were subsequently dipped in cinnamon leaf oil to incorporate into the polymer film. Under moderate acidic conditions of HCl medium, mass loss measurements of rectangular mild steel specimens embedded with cinnamon leaf oil, polypyrrole, and the combination of both over one-week period were obtained. The results revealed a superior corrosion inhibitory behaviour of the combined layer having the decreasing order of corrosion inhibition efficiency: polypyrrole and cinnamon leaf oil > polypyrrole > cinnamon leaf oil. Polarization resistance determined by electrochemical impedance spectroscopy, a more reliable method, further supports the strong corrosion inhibitory action of the combined layer on mild steel when compared to polypyrrole and cinnamon leaf oil alone. Open circuit potential measurements also indicate a lower corrosion rate when mild steel specimens are coated with the polymer and cinnamon leaf oil.
Magnetic field-induced deformation of castor oil-based ferrofluids
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Peradeniya ,Sri Lanka, 2024) Ratnayake, R. M. R.; Ranawaka, T. P.; Liyanage, J. P.
In the field of astronomy, optics is essential and adaptive optics is gaining prominence for its efficiency. This research includes the synthesis and characterization of a castor oil-based ferrofluid and the investigation of the magnetic field-induced deformation of ferrofluids and their potential as a base for liquid telescopes. Depending on the method of obtaining magnetic nanoparticles, the rheological behaviour of the ferrofluid changes significantly. Therefore, to obtain sufficiently small particles, pH level and temperature control were explored. This study proposes a novel surfactant coating method using castor oil as an alternative to oleic acid, given its ricinoleic acid content, which is chemically similar to oleic acid. Castor oil and kerosene are used as carrier liquids, with subsequent characterization of their magnetic and rheological properties. The ferrofluid particle size was studied with scanning electron microscopy (SEM). The rheological properties were studied using Rosensweig instability peaks under the precisely controlled magnetic field of a cavity magnetron electromagnet. The deformation was monitored using optical microscopy and analysed to understand the correlations between the magnetic field characteristics and the resulting deformation patterns. Based on the characterization, the pH control method proved better for obtaining smaller particles, as indicated by the sedimentation rate and confirmed by SEM data. This demonstrated that castor oil is a viable alternative to oleic acid, providing a stable base for ferrofluids that respond effectively to magnetic fields. Castor oil as the carrier liquid proved more stable due to longer response time and stable modelled surfaces. Kerosene, which was more volatile but was more rapid in response to the change in magnetic field, achieving faster response time. Data obtained were modelled using MATLAB, revealing the ferrofluids deformed relative to magnetic field strength. The outcomes of this study may be used as leverage for future studies on tunable liquid surfaces.
Prevalence of depression among undergraduate students: a case study of first-year undergraduates of a university in Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11) Gunarathna, Y. R. I. A.; Fernando, W. B. N. T.; Tennakoon, S. U. B.
University undergraduates are an important group of people for the future of a country. Therefore, their mental health is an important health concern. Students in the first academic year are at the threshold of the profession-targeted education where the transformation of the education system from school education to university education occurs. Depression is a common and serious mental disorder that affects nearly 300 million people worldwide. It may lead to a variety of emotional and physical problems among university undergraduates. It is found that depression causes people to feel a loss of energy, a change in appetite, sleep more or less, anxiety, reduced concentration, indecisiveness, restlessness, feelings of worthlessness, guilt, hopelessness and thoughts of self-harm or suicide. The objective of this study was to evaluate the prevalence of depression among first-year undergraduates. Additionally, it was focused on finding any significant associations between depression and its contributing factors. A cross-sectional study based on a self-administered questionnaire which contained questions to gather information on age, gender, hometown, type of accommodation, satisfaction with the degree program following, economic status, physical activities, alcohol and substance usage and relationship status was used on a random sample of undergraduates from the first academic year of nine faculties in a state university. The Peradeniya Depression Scale (PDS) was used along with the socio-demographic questionnaire to detect depression and factors associated with it among undergraduates. A total of 354 undergraduates participated in the study, and the overall prevalence of depression among them was 9.0% (n = 32). According to the Chi-square test, depression was found to be significantly associated with a diminished level of satisfaction with the enrolled degree program (p = 0.010) and lower monthly income of the family (p = 0.047). A higher percentage of daily drug users (daily liquor users 28.5%, daily smokers 18.7% and 33.3% of daily other drug users) were found to be depressed. Further studies need to be conducted to identify other factors associated with depression. It is recommended to implement scheduled systematic screening for depression and promote counselling services among undergraduates.
Air quality assessment using gas sensors in urban traffic areas in Peradeniya, Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Prasadani, S. A. N.; Ranathunga, R. J. K. U.; Thalpavila, T. K. N. D.; Navarathne, J. M. S. G. B.; Wijesinghe, M. B.
The issue of air quality is a pressing environmental concern, as 99% of the global population resides in areas where air quality standard levels are not met. Onsite and real-time air quality monitoring is required to ensure the respiratory health of the urban population. However, air quality monitoring is difficult to achieve using benchtop equipment such as gas chromatography and mass spectrometry. The primary emphasis of this research was to systematically explore and assess pollution levels by using portable gas sensors in urban areas in Peradeniya, thereby contributing valuable insights to the existing body of knowledge on environmental monitoring in this area. The study analysed NO₂, CO₂, and CO gas levels at designated monitoring locations. The analysis examined the effects of traffic density, time variability, road infrastructure, and environmental conditions. The monitoring device was developed by integrating hardware components with Arduino IDE software. The results implied that emissions from road traffic have a greater influence on CO₂, CO, and NO₂ concentrations than meteorological conditions. The levels of pollution were found to be elevated by approximately 100% in traffic locations, which is a 25% increase compared to normal traffic conditions. The observed trends showed a 20% increase in pollutant gasses in the afternoon and evening. Galaha junction had an approximate 40% increment than Gatambe, and it demonstrates that the pollution levels have varied significantly within short distances. The levels of all three gases were higher at the Galaha and Gatambe junctions compared to the reference location, University ground. Afternoon hours showed higher pollution levels, which were affected by high ambient temperature. Analysis of the present study was limited to a specific area, which may limit the generalizability of the results to overall air pollution and potentially restrict the applicability of findings to urban traffic areas. Further investigations, including multiple geographic locations in the Kandy and Peradeniya areas, are being conducted to calibrate the developed detection system to measure gas concentrations in ppm.
Toxic trace elements (Cadmium and Arsenic) in Sri Lankan commercial rice (Oryza sativa L.)
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Gunawardana, J. W.; Perera, I. C.; Wageesha, N. D. A.; Witharana, C.; Gunawardena, S. A.
Toxic trace element (TTE) contamination in dietary items, such as rice (Oryza sativa L.), poses a significant food safety concern, as even trace amounts of these elements can be harmful to human health. The bioavailability of TTEs is closely monitored in many countries to ensure compliance with statutory toxicological threshold values and permissible levels. This study investigated the presence of cadmium (Cd) and arsenic (As) in commonly consumed Sri Lankan rice varieties and assessed the potential for chronic dietary exposure to these toxic trace elements through rice consumption. A total of 54 (N = 54) husked rice, representing the ten most commonly consumed varieties in Sri Lanka, were sampled at selected dedicated economic centres, from which 25 (n = 25) analytical composites were homogenized, lyophilized and stored at -20 °C. An analytical portion of ~ 0.2 g lyophilized grain powders underwent microwave-assisted high-pressure acid digestion and was profiled using inductively coupled plasma mass spectrometry. Results were expressed as mg/kg on a wet-weight basis (mg/kg ww). Toxicological assessment was conducted using WHO-JECFA Codex Alimentarius Maximum Permissible Values, Provisional Tolerable Monthly Intake (CodexPTMI) and European Food Safety Authority guidelines (EFSATWI) considering national per-capita consumption rates. The mean ± SD and median (IQR) Cd and As concentrations of rice grains were 0.126 ± 0.417, 0.033 (0.063) and 0.055 ± 0.030, 0.050 (0.036) mg/kg ww, respectively, which were below the Codex MPLs. Only one sample exceeded the Codex PTMI for Cd. Twenty percent of samples exceeded the Cd-TWIEFSA, indicating potential chronic dietary exposure to Cd. The red pericarp grains accumulated higher amounts of both Cd and As than the white pericarp varieties (pCd, pAs > 0.05). Traditional varieties showed lower As (pAs > 0.05) but higher Cd values (pCd > 0.05) compared to improved varieties. The parboiled grains of “Nadu” and “Samba” had higher element concentrations than the non-parboiled “Kekulu” varieties, irrespective of the pericarp colour. Approximately 20% of rice samples in Sri Lanka, especially among the red pericarp and improved varieties, exceeded the EFSA threshold for Cd.
Anti-diabetic, anti-inflammatory and GC-MS profile analysis of Schleichera oleosa (Kon) seed extract
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Senaweera, Y. T.; Darmasiri, N. H.; Shanuke, D. S.; Molagoda, M. N.; Ranasinghe, P.; Jayasooriya, P. T.; Samarakoon, K. W.
The medicinal properties of Schleichera oleosa (Lour.) Oken, commonly called “Kon”, has been acknowledged and utilised in traditional medicine for its wide-ranging therapeutic effects. This study was carried out to determine the fatty acid content in S. oleosa seeds. Gas Chromatography-Mass Spectroscopy (GC-MS) was employed to identify and quantify fatty acid content, while its biological activities were determined using Alpha-amylase inhibition using the dinitrosalicylic acid (DNS) method. Anti-inflammatory activity was assessed by bovine serum albumin method for the methanolic extract, as well as for the hexane, ethyl acetate and aqueous fractions. The results were expressed as mean ± SD using GraphPad Prism 7.4 (n = 3). The results were analysed by one-way ANOVA followed by Tukey’s multiple comparison tests, and p < 0.05 was considered statistically significant. The analysis identified 13 major fatty acids, with Eicosanoic acid exhibiting the highest significant percentage (39.16 ± 5.64). 9-Octadecenoic acid, Hexadecanoic acid and 9,12-Octadecadienoic acid were also detected as 36.81% ± 2.39, 10.84% ± 1.40 and 6.98% ± 2.29, respectively. The anti-inflammatory potential of S. oleosa seed extract was significant, while no antidiabetic activity was observed against the alpha-amylase enzyme. The crude methanolic seed extract exhibited better anti-inflammatory activity at 81.68 ± 0.45 due to the presence of Eicosanoic acid and other fatty acid derivatives, with 82.34 ± 0.22 for Diclofenac as the standard. Our results suggest that S. oleosa seed extract is a promising source of natural compounds with anti-inflammatory properties, making it suitable for potential therapeutic, nutraceutical, and functional food applications.
Effect of rice variety on reproductive success and grain consumption of maize weevils, Sitophilus zeamais (Coleoptera: Curculionidae): a preliminary study
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Patabendige, A. P. K. Y.; Wanasinghe, W. M. T. D.; De Silva, W. A. P. P.; Weeraratne, T. C.
Sitophilus zeamais (Motschulsky, 1855), commonly known as the maize weevil, is a destructive pest that frequently occurs in stored grains, including rice. The substrate variety can affect the reproductive success and population dynamics of these pests. The aim of this study was to investigate the effect of rice variety on the reproductive success of S. zeamais and to evaluate the rate of consumption of rice by S. zeamais. The eleven rice varieties in Sri Lanka, including four organic and seven non-organic, were used. Three pairs of newly emerged S. zeamais were introduced into 20 g of disinfected rice of each variety per replicate (3 replicates per rice variety) and observed for one month. Except for “Suwandal” (9 individuals), the total number of weevils in organic rice was relatively high, with an average of 72, 53, and 18 from “Kuruluthuda”, “Pachchaperumal”, and “Maavi”, respectively. The highest average weight loss of organic grains was observed in “Kuruluthuda” (4.64%). Regardless of the progeny size, the weight loss in “Pachchaperumal” and “Maavi” was almost similar (~ 2.5%). The results revealed that the reproductive success of S. zeamais was low in non-organic varieties compared to organic (p = 0.019), except “Samba”, which showed a considerable population after one month (n = 9 weevils) with 0.36% weight loss. The total number of weevils observed in “Red-raw rice”, “White-basmati”, and “Naadu” were 7, 7, and 6, respectively. No population increase was reported in “Red-basmati”, “Keerisamba”, and “White-raw rice”. Except for Samba, a non-considerable grain weight increase was observed in “White-basmati” (2.27%) and “White-raw rice” (1.34%), suggesting that the weight increase was due to the eggs laid by the introduced weevils. The study suggested that the organic rice varieties are more vulnerable to S. zeamais attacks, and chemicals used for storing grains delay the reproduction of S. zeamais.
Comparative evaluation of water hyacinth, vegetable waste and gliricidia as nitrogen sources for composting paddy husk
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Shamudika, H. U.; Nadeesha, M. A. Y. L.; Hewawasam, H. P. C. P.; Jayasanka, D. J.
Paddy husk is one of the most widely produced agricultural wastes in rice production. The co-composting of paddy husk is an effective method for addressing this waste issue. This study aimed to transform ordinary paddy husk into high-quality compost using water hyacinth (Eichhornia crassipes), vegetable waste, and gliricidia (Gliricidia sepium) as nitrogen sources. The quality of the compost was compared using pH, electrical conductivity (EC), organic carbon (C), total nitrogen (N), available phosphorus (P), and exchangeable potassium (K). The experiment followed a Completely Randomized Design (CRD) with four treatments: T1 = paddy husk only, T2 = paddy husk + water hyacinth, T3 = paddy husk + Gliricidia, and T4 = paddy husk + vegetable waste, mixed in a 1:1 ratio. The mixtures were aerobically decomposed using the compost pile method and analysed after 67 days. The results were compared with the compost standards provided by the Sri Lanka Standards Institution. A pot experiment was conducted to evaluate the effect of the prepared compost on the growth of water spinach (Ipomea aquatica). The pH values of all trials ranged between 6.5 and 7.9, and EC values ranged from 0.13 dS/m to 0.977 dS/m. The T2 compost mixture (paddy husk + water hyacinth) showed significantly higher (p < 0.05) levels of total nitrogen (1.15% ± 0.03) and potassium (0.466% ± 0.01) compared to other mixtures. The T3 compost mixture (paddy husk + gliricidia) exhibited the highest phosphorus level (1.33% ± 0.08). Low potassium levels were consistent across all compost mixtures. Considering the pH, EC, total nitrogen, and phosphorus levels obtained for the T2 mixture (pH 7.96, EC 0.977 dS/m, N 1.15%, and P 1.257%), along with the highest fresh weight (6.836g ± 0.373) and dry weight (0.6075g ± 0.037) of plant samples from the pot experiment, the compost mixture containing paddy husk and water hyacinth was found to be the most suitable for field application.
Predictive maintenance of quartz processing equipment using machine learning
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Nipunika, H. G.; Dassanayaka, S. M.; Dushyantha, N. P.
Sri Lanka's quartz industry plays a vital role in the country's mineral processing industry, accounting for US$ 8.38 million in export earnings in 2023. However, the inefficiencies and machine downtime of the heavy-duty machinery challenge the overall performance of the industry. To address these issues, this feasibility study aimed to apply Machine learning (ML) to implement predictive maintenance in quartz processing machinery, particularly for crushers, mills, and classifiers. The study was structured into two principal phases: digital model development and model implementation. A synthetic dataset was created to simulate sensor readings, including temperature, vibration levels, and running hours, enabling the training of a Random Forest Classifier. Initial results revealed that running hours and temperature were the most significant predictors of machine failure. Since the damping mechanisms in heavy-duty machines absorb vibration, it has a lesser impact. The confusion matrix revealed that the model is more effective in predicting where no maintenance is needed. Further cross-validation with real-world data will be essential to strengthen the model’s strength, assessing potential cost savings from downtime reduction and maintenance optimization. By deploying this ML-based model in the real world, the potential operational efficiency in Sri Lanka’s quartz industry will be enhanced. This approach could integrate automation into the mineral processing industry, aligning with global trends to improve productivity and reduce maintenance costs of heavy-duty machinery.
Reduced order model for breast cancer detection
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Subawickrama, H. D. A. W.; Udagedara, U. G. I. G. K.; Nishantha, S. A. A.
Breast cancer often starts in the milk ducts or glandular lobules. According to the World Health Organization, there are about 2.3 million new cases and over 600,000 deaths annually. In Sri Lanka, around 3,000 new cases are diagnosed yearly, highlighting the need for better detection methods. Imaging techniques have limitations, like reduced sensitivity in dense breast tissue and potential false positives, which means dataset features may not always effectively capture crucial information for detecting breast cancer. This study presents a dimensional reduction process using Principal Component Analysis (PCA), a powerful technique for feature selection and dimensionality reduction, particularly effective with large datasets. This study aimed to create a low-dimensional model that can be used to classify breast cancers accurately. A benchmark dataset called Wisconsin Diagnostic Breast Cancer (WDBC) was used for data preprocessing and creating a reduced-order model using PCA. The performance of the reduced order model was evaluated by reconstructing the original data using the selected principal components and assessing the accuracy of this reconstructed data. The reconstruction error was measured using the Mean Squared Error (MSE) metric. The scree plot revealed a notable difference in the percentage of correctly reconstructed benign and malignant cases when selecting principal components 1 and 2, highlighting a substantial drop in variance. However, when choosing between 3 to 30 components, the percentages of correctly reconstructed benign and malignant cases remained consistent at 70.78% and 29.22%, respectively. These values are identical to the class distributions observed from the original data. Ten principal components were selected for model reduction, resulting in a reconstruction error of 0.0002 MSE. This low error value reflects a very accurate reconstruction from the reduced dimensions. These findings suggest the capability of the reduced order model to identify benign and malignant cases, which can be further used for investigations with high dimensional and complex data.
Cause and effect analysis of impacts of land cover changes on Belihuloya mini-catchment area
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Gunathilake, L. W. I.; Jayawardhana, D. T.; Chandrasekara, C. M. K. N. K.
The rapid expansion of human activities has significantly transformed landscapes, leading to major impacts on water resources and ecosystem health. This study comprehensively assessed the transformations within the Belihuloya mini catchment, focusing on the effects of land use and land cover changes. The primary objectives included identifying changes, analyzing trends, and evaluating human perceptions of the impacts on the mini catchment. The study utilised remotely sensed data from 1959, 1988, 2000, and 2020 to assess land use and cover changes over time. A questionnaire survey was conducted among 60 randomly selected households across six Grama Niladhari Divisions within the catchment area. Correlation-based pair-wise analysis, paired t-test analysis, vulnerability value calculation, and interpolation mapping were employed to interpret the data. A cause-and-effect analysis was conducted using the Drivers-Pressures-State-Impacts-Responses (DPSIR) framework. The results revealed significant changes in land cover and use over the study period. Forest cover decreased dramatically, from 80% in 1959 to 33% in 1988, primarily due to the expansion of paddy fields and home gardens. Nine major driving forces were identified, highlighting the pressures on the natural environment and wildlife from land and forest clearance for construction. High-altitude areas surrounding the young Belihuloya river faces significant risk due to rapid land use changes, threatening the river's energy flow. The southern region, including Sabaragamuwa University and the Samanalawewa reservoir, is equally vulnerable, potentially compromising the mini-catchment's health. The findings underscore the urgent need for conservation efforts and informed land management practices to mitigate adverse impacts on the mini-catchment ecosystem and ensure sustainable development for future generations.
Antioxidant potential of bark column fractions of Stereospermum suaveolens
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Thanusika, N.; Aluthge, D. C.
Antioxidants are molecules that primarily slow down or prevent oxidation reactions. Their application in pharmacology is valuable to improve current treatments for diseases. Medicinal plants are a rich source of biologically active compounds such as flavonoids, phenolic compounds, etc., which may be responsible for their antioxidant activities. This study aimed to investigate the antioxidant activity of the column chromatographic fractions of crude extracts of Stereospermum suaveolens bark. The extraction was performed using ultrasound sonication, followed by fractionation with silica gel column chromatography. The antioxidant activity test was carried out using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay with 200 μg/mL fraction solutions, and L-Ascorbic acid was used as the standard. Thin-layer chromatography was performed to analyse the chemical profile. Methanolic bark extracts of S. suaveolens yielded seven fractions, with radical scavenging percentages ranging from 13.22% to 82.51%. The test results further depicted that the third and fourth fractions possessed high antioxidant activities with the percentage radical scavenging activity of 82.51% and 56.27%, respectively, whereas other fractions showed weak antioxidant activities. However, the standard L-Ascorbic acid exhibited the highest antioxidant activity compared to bark fractions (92.83%). However, the radical scavenging activities of all active bark fractions were lower than that of L-Ascorbic acid as a positive control. The study concluded that most active fractions demonstrated good antioxidant activity, worthy for further study to isolate specific compound/s which is/are responsible for antioxidant activity.
Biofilm biofertilizer-based modern bio-organo-mineral fertilizer practices unveil the potential for organic rice cultivation
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Jayasekara, A. J. M. S. H.; Premarathna, M.; Seneviratne, G.; Madawala, H. M. S. P.; Nanayakkara, B. S.
Rice (Oryza sativa L.) cultivation in Sri Lanka heavily relies on chemical fertilizers (CF), which raises significant concerns for both human health and the environment. This study investigated the effect of biofilm biofertilizer (BFBF)-based modern bio-organo-mineral fertilizers (BOMF) on the growth and yield of rice in organic farming. Field trials were conducted in Anuradhapura, Puttalam, Polonnaruwa, and Ampara districts in Sri Lanka, employing four treatments i.e. (a) BOMF practice (500 kg NPK BOMF/ha + 2.5 L BFBF/ha), (b) hybrid practice (225 kg PK BOMF/ha) + CF N (62.5 kg/ha) + (2.5 L BFBF/ha), (c) CF practice (340 kg CF NPK/ha, as recommended by the Department of Agriculture, Sri Lanka), and (d) control (no fertilizer) in a complete block design with three replicates in each location. Plant samples were collected at the 50% flowering stage and analysed for shoot dry weight (SDW) and root dry weight (RDW). Grain yield was measured at harvest. After confirming the normality of the data, ANOVA followed by Tukey’s HSD test was performed to compare the means. The results revealed a significantly (p < 0.05) higher yield (9,056 kg dry weight/ha) produced by the hybrid practice, while BOMF (5,874 kg dry weight/ha) and CF (5,394 kg dry weight/ha) practices produced comparable yields. As such, the hybrid practice showed about 67% increase in grain yield compared to the CF practice. In addition, the two practices with BOMF showed significantly (p < 0.05) higher RDWs compared to the CF practice and the control, with no differences in SDWs across the treatments. In conclusion, BOMF practice exhibited the potential to replace the conventional CF-only practice to mitigate some consequences of the high usage of CF in rice cultivation. Comprehensive field trials are required to confirm these findings.
Fifth-order Runge-Kutta method for solving quadratic Riccati equation
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Jayasinghe, B. H. O.; Gunarathna, W. A.; Mohamed, M. A. M.
The quadratic Riccati Differential Equation (RDE), a non-linear ordinary differential equation, has found numerous applications in many fields including biology, finance, and engineering. Solving the RDE analytically is challenging due to several reasons such as the lack of closed-form solutions, complex solution forms, and singularity issues. Numerical methods are often preferred for solving RDE. The initial-value problem for RDE, denoted by IVPRDE, with the initial condition 𝑦(𝑡0)=𝛼∈ℝ, is given by 𝑦′(𝑡)=𝑝(𝑡)+𝑞(𝑡)𝑦+𝑟(𝑡)𝑦2=𝑓(𝑡,𝑦), where 𝑝(𝑡),𝑞(𝑡), and 𝑟(𝑡)(≠0) are continuous functions defined on the interval [𝑡0,𝑇]. Recently, the classical fourth-order Runge-Kutta (RK4) method has been applied to obtain numerical solutions for IVPRDE, establishing its stability and convergence. In literature, higher-order (>4) Runge-Kutta methods have not yet been applied to solve the IVPRDE. This study aimed to apply a fifth-order Runge-Kutta method, specifically Butcher’s fifth-order Runge-Kutta (BRK5) approximation, to numerically solve the IVPRDE and obtain its numerical solutions. The stability and convergence of the proposed method were established. Using BRK5, maximum errors on a discretized domain of [𝑡0,𝑇] with different uniform grid sizes (ℎ) were computed and compared with those of RK4 method for four numerical test examples. Numerical results demonstrate that BRK5 has a superior accuracy over RK4. For example, when ℎ=0.01, the maximum errors due to BRK5 for the tests are 3.1086e-15, 1.8797e-12, 8.8818e-16, and 7.4052e-14, whereas the corresponding errors computed by RK4 are 2.6645e-15, 1.4105e-09, 6.5340e-10, and 6.7954e-11. These results verify the effectiveness of BRK5 over RK4 for solving IVPRDE.
Temporal and spatial changes in vegetation cover of Mahaweli-h system: Mahaweli development project (1988 to 2022)
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Ariyasingha, U. D. H. P.; Chandrathilake, G. G. T.; Kumara, M. A.
The Mahaweli development project is Sri Lanka's largest and most significant multi-purpose development initiative, covering an extensive area of 57,225 × 104 m² within the Mahaweli H zone. This project has profoundly impacted vegetation cover in the Mahaweli H System, prompting a study of the temporal and spatial changes since its initiation in 1988. This research aimed to assess these changes across the entire Mahaweli H System from 1988 to 2022 and included a trend analysis of vegetation health and conservation efforts within five forest reserves and one wildlife boundary. Data from 1988 to 2022 were analysed, with projections extending to 2042. The period was divided into five-year intervals, and satellite images from the Landsat 5 TM and the Landsat 8 OLI/TIRS were processed using ArcGIS software. Indices were classified using the natural breaks (Jenks) method, facilitating land size determination. A linear regression model was applied to analyse trends in five forest reserves (Licolawewa Upper, Lunuoya, Yoda Ela, Licolawewa Lower, and Bongamuwa) and one wildlife boundary from 1988 to 2042. The overall vegetation area exhibited fluctuations, notably decreasing to 9,980 × 104 m² from 1993-1997, followed by a recovery peaking at 20,230 × 104 m² from 2018-2022. The linear regression analysis of NDVI trends in ArcGIS revealed a positive trend in the Licolawewa Upper and Lunuoya Forest Reserves, as well as in the Wildlife boundary, indicating improved vegetation health and effective conservation efforts. Conversely, the Yoda Ela, Licolawewa Lower, and Bongamuwa forest reserves exhibited negative trends, indicating a decline in vegetation health. The study underscores the importance of continuous monitoring and sustainable land management practices to ensure the long-term health and conservation of vegetation in the Mahaweli H System.
Network-based investigation into tuberculosis spread in Nuwara Eliya District, Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Perera, P. N. M.; Perera, K. K. K. R.
Tuberculosis (TB) remains a major health challenge in low- and middle-income countries like Sri Lanka, requiring ongoing control and elimination efforts. This study focussed on the Nuwara Eliya District, a popular tourist destination that highlights the need for targeted TB control measures due to the high number of visitors. The primary objective was to forecast TB patients for 2024 by gender, age group, and TB type using ARIMA models for descriptive analysis while constructing a synthetic dataset that includes gender, age, TB type, and relationship based on the forecast results. This dataset was validated through k-fold cross-validations and then converted into a network, where the nodes represent patients and edges represent patient contact relationships. The constructed network was analysed using centrality measures, cluster analysis, and Technique for Order of Preference by Similarity to the Ideal Solution (TOPSIS) methods. Data collection involved annual data from 2012 to 2021 obtained from the National Programme for Tuberculosis Control and Chest Disease website and primary data from Nuwara Eliya Hospital for 2022 and 2023. The ARIMA model was applied solely for forecasting. The synthetic dataset constructed by taking percentages of forecasting data, underwent k-fold cross-validation, achieving an accuracy of approximately 66.39%, supporting the reliability of the forecasting model. Centrality analysis identified influential nodes crucial for disease transmission, while cluster analysis revealed low local clustering but a robust community structure, suggesting that targeted interventions within specific groups could enhance TB control efforts. The TOPSIS method ranked the top ten most influential patients, offering strategic targets for intervention. These findings underscore the importance of tailored control measures to effectively manage TB in high-visitor areas.
Enhancing pitch detection by developing methods of time-frequency analysis
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Egodawele, K. D. K.; Ranasinghe, P. G. R. S.
Time-frequency analysis is an indispensable technique for understanding the dynamics of signals over time, providing insights into instantaneous occurrences, temporal patterns, and hidden structures within complex data. In the present study, the methods of time-frequency analysis were used for a qualitative analysis of music signals. The Short Time Fourier Transformation (STFT) and Continuous Wavelet Transformation (CWT) were investigated for qualitative analysis of music signals. Digital Signal Processing (DSP) is vital in studying the accuracy of the conversion from analog signals to digital signals, minimizing potential errors that could be generated in the process. The primary contribution of this work was the introduction of a novel “Hann-Kaiser window” for the short-time Fourier transformation, which enhances pitch detection and reduces spectral leakage. This window combines the attributes of the Hann window and Kaiser window, resulting in better frequency resolution and reduced leakage compared to traditional windows. The efficiency of the modified window function was evaluated using specific parameters, including Signal-to-Noise Ratio (SNR), main-lobe width, and side-lobe suppression. The spectrograms revealed sharper pitch differentiation, particularly in harmonically rich regions of the signal, while the scalograms provided detailed insights into the transient features of the music signal. These visualizations demonstrated the Hann-Kaiser window’s ability to enhance the clarity of individual frequency components, making it easier to track pitch variations over time. The implementations of time-frequency representations were performed using Python, generating spectrograms and scalograms. Building on these results, future research directions could focus on integrating these time-frequency analysis methods into music signal processing workflows, further refining the accuracy of pitch detection.
Agave americana as a promising green biosorbent for Ni(II) remediation
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Wickramasinghe, W. R. M. N. R.; Karunathilaka, R. M. M. K.; Priyantha, N.
The heavy metal content in the environment has been rising due to industrial advancement. Nickel (Ni) poses adverse health impacts, such as gastrointestinal distress, pulmonary fibrosis, and skin dermatitis, when present in excess, although it is a micronutrient essential for cellular functions. Excess Ni(II) concentrations can also induce ecological damage by disrupting the cellular functions of flora and fauna. Therefore, Ni remediation from industrial effluent is essential to safeguard human quality of life and ecosystem health. Fibrous biosorbents present promising green alternatives compared to other biosorbent types, offering advantages such as ease of surface modification to attract intended contaminants and simple removal. This study aimed to conduct a comprehensive investigation of the adsorption characteristics of Ni(II) on Agave americana fibres as a value-added product. Batch experiments were conducted under optimal parameters; 40 min shaking time, 20 min settling time, and ambient pH, which indicated a significant removal rate of 90.39% at an agitation speed of 150 rpm and room temperature with an optimum dosage of 20 g/L of the sorbent. Kinetic studies validated the pseudo-second-order model for the adsorption of Ni(II) on Agave americana fibre, with regression coefficients of 0.9968 and 0.9726 at ambient pH and initial solution pH of 4, respectively, suggesting that chemisorption is the rate-limiting factor in adsorption. Moreover, the fitting of kinetic data to the Weber-Morris intra-particle diffusion model at ambient pH and initial solution pH of 4 implied that both intra-particle diffusion and the boundary layer can affect the rate of adsorption. Further studies could expand the scope of Ni remediation from industrial effluent on a larger scale.
Bioactivities of methanolic leaf extracts of Adenanthera pavonina, Cynometra cauliflora and Dregea volubilis
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2024-11-01) Bowaddeniya, U. G. W. S.; Kalinga, J.; Piyasena, N.; Marikkar, J. M. N.; Adikaram, N. K. B.; Jayasinghe, L.
This study determines the bioactivities of the leaves of three abundantly distributed plants in Sri Lanka. Healthy leaves of Cynometra cauliflora (Fabaceae: “Naminan”), Adenanthera pavonina (Fabaceae: “Madatiya”) and Dregea volubilis (Apocynaceae: “Anguna”) were collected from Kandy District. The collected leaves were shade-dried, ground and extracted into methanol by sonication. Antioxidant ability by 2-2–Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and Ferric Reducing Antioxidant Power (FRAP) assays, α-Amylase inhibitory activity, cytotoxicity against brine shrimps and phytotoxicity against lettuce seed germination were assessed for a concentration series ranging from 2000 mg/L to 31.25 mg/L. All assays were triplicated. Results of the DPPH radical scavenging assay revealed C. cauliflora has relatively strong activity (IC₅₀ 7.19 ± 0.15 mg/L) compared to the positive control: ascorbic acid (IC₅₀ 1.97 ± 0.02 mg/L), whereas A. pavonina (IC₅₀ 248.64 ± 0.02 mg/L) and D. volubilis (IC₅₀ 361.40 ± 0.09 mg/L) extracts showed moderate activities. Compared to the FRAP of positive control, Trolox (12.07 ± 0.03 μmol of FeSO₄/mg of the sample), the highest FRAP was observed in C. cauliflora (4.28 ± 0.02 μmol of FeSO₄/mg) followed by A. pavonina (0.05 ± 0.03 μmol of FeSO₄/mg) and D. volubilis (0.04 ± 0.03 μmol of FeSO₄/mg). Cynometra cauliflora (IC₅₀134.29 ± 5.24 mg/L) and A. pavonina leaves (IC₅₀ 365.03 ± 4.57 mg/L) have strong α-amylase inhibition potential compared with the IC₅₀ of positive control: acarbose (45.99 ± 3.97 mg/L) whereas, D. volubilis resulted a weak activity (> 2000 mg/L). In the brine shrimp lethality assay, C. cauliflora, A. pavonina, and D. volubilis showed LC₅₀ of 880.07 ± 0.15 mg/L, 1900.42 ± 0.08 mg/L, and 109.95 ± 0.13 mg/L respectively. K₂Cr₂O₇ (LC₅₀ 35.16 ± 0.03 mg/L) was used as the positive control. In lettuce seed germination assay, compared to the inhibition of abscisic acid (shoot inhibition IC₅₀ 0.99 ± 0.35 mg/L, root inhibition IC₅₀ 1.11 ± 0.50 mg/L), only C. cauliflora resulted a moderate root inhibition (523.22 ± 0.05 mg/L) while other two extracts showed a weak inhibition (> 2000 mg/L). None of the crude extracts resulted an inhibition in the shoot elongation. Results from all assays were significantly different from the positive controls. However, as crude leaf extracts of C. cauliflora and A. pavonina may contain potent anti-diabetic compounds due to the strong potential to inhibit α-amylase enzyme.

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