Research Papers - School of Natural Sciences
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Publication Open Access Porous carbon materials in biomedical applications(2019-11-12) Thambiliyagodage, C. J; Mirihana, S; Gunathilaka, HRecent advances in carbon based porous materials in biomedical science and technology have been discussed. Biomedical applications like drug delivery, tissue engineering, biomedicine, gene transfection, photothermal and photo-dynamic theory of porous carbon materials such as mesoporous carbon materials, carbon nanotubes, activated carbon, graphene and fullerenes have been briefed. Finally, future biomedical applications of new porous carbon materials including metal organic frameworks, carbon dots have been introduced in this mini review.Publication Open Access Eco-friendly porous carbon materials for wastewater treatment(Springer, Singapore, 2019-08-07) Thambiliyagodage, C. J; Cooray, V. Y; Perera, I. N; Wijesekera, R. DDifferent porous carbon materials were applied to remove organic compounds and heavy metals from wastewater. Hierarchically, porous nitrogen rich monolithic carbon (HPC) was synthesized through the sol-gel synthesis method and carbonization process. Rice husk (RH), an agricultural waste material followed by carbonization at two different temperatures (RH400 and RH600) was used as the naturally generated porous carbon composite. Activated carbon (AC) was used as the control. According to the FT-IR spectra, different functional groups are present in all adsorbents. Scanning electron microscopic (SEM) images show an irregular shaped, random disordered macropore structure in RH and a robust sponge-like disordered macropore structure with ligaments in HPC. Transmission electron microscopic (TEM) images of these materials show a disordered mesopore network. Adsorption capacities of these porous carbon materials were determined for organic dyes and metal ions. Methylene blue and Methyl orange were used as the model organic compounds and Pb2+, Cu2+, Ni2+, and Cd2+ ions were selected as the metal ions. The experimental data demonstrate that the adsorption capacity of AC for Methyl orange (5.88 mg/g) is much higher than that of the alternatives (RH400–1.97 mg/g, RH600–0.69 mg/g, and HPC – 1.14 mg/g). Adsorption capacity of all the adsorbents for Methylene blue is quite similar. Adsorption capacity of RH400 for Pb2+ is much higher than that of RH600, AC and HPC. RH400 has a greater adsorption for Cu2+ and Ni2+ than the other adsorbents. All adsorbents show a low adsorption capacity for Cd2+. RH400 is a promising adsorbent for wastewater purification.Publication Embargo Catalytic graphitization in nanocast carbon monoliths by iron, cobalt and nickel nanoparticles(Pergamon, 2018-08-01) Thambiliyagodage, C. J; Ulrich, S; Araujo, P. T; Bakker, M. GHierarchically porous carbon monoliths containing metal (Fe, Co, Ni) nanoparticles were synthesized in a one-pot synthesis through a nanocasting technique using silica (SiO2) as the template. The macropore structure of SiO2 has been replicated in nanocast carbon and N2 adsorption analysis shows that the monoliths have high surface area, high mesopore volume, and that micropores are also present. The temperature effect on catalytic graphitization was studied by using x-ray diffraction (XRD), transmission electron microscope (TEM) and Raman spectroscopy. It is observed that iron was capable of producing turbostratic carbon at 500 °C, while turbostratic carbon was produced at temperatures of 700 °C when cobalt and nickel are present. Iron, cobalt, and nickel were found to be good graphitization catalysts with the order of catalytic activity being iron > cobalt > nickel. Raman spectroscopy experiments provide insight into the degree of ordering of the carbon of each sample and are in agreement with the results from the other techniques: with increasing pyrolysis temperature, with and without the presence of metals, ordering of amorphous carbon is confirmed. Detailed analysis of the Raman spectroscopic data showed clear differences between the metal catalyzed and non-catalyzed samples enabling the contributions from the two different mechanisms to be clearly distinguished.Publication Open Access THE USE OF BLOOM’S TAXONOMY TO ASSESS STUDENTS’ PERFORMANCE EFFECTIVELY IN WRITTEN EXAMINATIONS(2017) Peiris, S; Peiris, C. N; Wickramasinghe, SBloom’s Taxonomy is widely used, to bring out thinking ability in students, as an assessment method. In this article we emphasize four types of methods generally used in evaluating the intended learning outcomes in written examinations. How questions should be structured in each level of cognitive domain is discussed with an example in multiple choice questions (MCQ), short answer question (SAQ), structured type questions (STQ) and essay type questions (ETQ). Common biological applications were used as example questions. The questions were developed to show how students’ thinking ability was brought out when questions were structured in line with the levels of cognitive domain in Bloom’s Taxonomy. In conclusion, this paper defines how the application of Bloom’s Taxonomy helps in developing complete answers which come out not from the students’ memory but from applying, analyzing, synthesizing and evaluating.Publication Open Access GUIDANCE FOR PERFORMING TEACHER SELF-EVALUATION IN ORDER TO ENHANCE THE QUALITY OF TEACHING AT HIGHER EDUCATION INSTITUTIONS IN THE ASIA-PACIFIC REGIONS(Asia-Pacific Quality Network, 2017) Jayakodyarachchi, D. K; Jayatilake, H. H; Malalage, B. A; Peiris, C. NAdaptation to globalization and diversification in Higher Education opens new horizons and leads to re-engineering of the existing higher education (both teaching and learning) in order to cope with the expanding scope and differences. Consequently, Higher Educational Institutes (HEIs) will need to adopt new theories and practices to dissolve the boundaries of quality in HE. The Internal Quality Assurance subdivitions of HEIs play an important role in these processes and will need to focus on and guide the ‗enhancement‘ of teaching and learning quality. This enhancement could be achieved by a variety of ways with the aim to develop quality in teachers. This is bound to result in the quality of the teaching process. When developing the quality in teachers‘, it is vitally important to have positive perceptions towards the changing needs. Thus, the Teacher Self Evaluation method (TSE) directly helps individuals improve their perceptions in the positive way and thereby achieve most of the characteristics of a quality teacher. Therefore the guidelines of good practices applicable to IQA units/evaluators for effective teacher evaluations/assessments ,the characteristics of a quality teacher, the enhancement of the teaching quality at HEIs in the AsiaPacific regions as well as the issues which disrupt the TSE have become vitally important for the teaching practice.Publication Open Access A case study on identification and assessment of postharvest losses of tomato (Lycoperisicon escuentum Mill)(Postgraduate Institute of Agriculture, University of Peradeniya: Peradeniya, 1992) Rupasinghe, H. P. V; Peiris, C. N; Wijeratnam, R. S. WA study was undertaken to quantify and identify the causes of the postharvest losses of tomato during the Malta season of 1991. In the first phase of the study a suivey was earned out using random samples to collect information on the present system of posthaivest handling of tomato. Four major stages of the posthaivest marketing sequence were identified, namely; fann gate, collection agent, Manning wholesale market (Colombo) and exporter respectively. Loss assessments were conducted at these stages. Tlie survey revealed that pest and diseases such as pod borrer (Heliolhis zea) attack and blight (Altemuiia solani and Pliyiopluliora infestans) are the major contributions for posthaivest losses at the fann gate. Over maturity at hanest, bird attack and losses due to sun scorch were also obseived. Cultivating small extents of land (66% of farmers possess less than half acre) increases the liaircsting interval which resulted in a high percentage of over maturity. Tlie above factors subsequently made considerable losses at the collection agents when soiling the product for transportation. Significant losses were observed al the Manning market due to long distance of transportation with improper handling and transportation. Tlte main problem with exporters was the lack of uniformity of product with respect to maturity and size. Cumulative loss at the Manning wholesale market was obseived to be close to 54%. Contributions to the major causes of loss were as follows; mechanical damage due to over ripening 17.3%, pod borrer attack 23%, blight 4.8% and mechanical damage due to other factors 15%. Tlie cumulative loss and rejections after export quality selection was as high as 96%. Rejects due to non conformity to export specifications with respect to maturity, size and shape were 27.52% and 7.34%, respectively.Publication Open Access Effect of packaging material on the storability of Chillie (Capsicum annum L.) seed in Sri Lanka(Postgraduate Institute of Agriculture, University of Peradeniya: Peradeniya, 1994) Silva, S. G. R; Peiris, C. NExtracted chillie seed from ripe, desiccated dry pods of cultivar MI 2 of known germination (81.0%), was dried to 9.7%, 5.9% moisture contents, and packed in three different packaging materials: aluminium foil, 500 gauge polythene and woven polypropylene sacks. The seeds were stored at ambient conditions in Pelwehera (30°C, 80% RH), Rahangala (23°C, 79% RH) and in a cold room (20°C 65% RH) in Gannoruwa. Seed germination, field emergence, and seed moisture content of the stored seed were tested at the inception and at 3 month intervals during the 12 month study period. Chillie seed with a low initial moisture content (5.9%) maintained germinability better than seeds with a high moisture content (9.7%) in all locations. Triple laminated aluminium foil was a better packaging material. Polysack packaging displayed free moisture movement from the early stages of the study, in all the locations. Polythene (500 gauge) was better than polysack and similar to aluminum foil when storing low moisture (5.9%) chillie seed for 12 months, at all the locations except in Pelwehera. A cold room condition was the best to store chillie seed without losing its viability below 75% for a period of one year. It could be recommended that these dried, extracted chillie seed from ripe dry pods of cultivar MI 2 packed in aluminium foil or in polythene (500 gauge) be stored in a cold room (20PC, 65% RH) for a long term (12 months).Publication Open Access Identification of cowpea cultivars (Vigna unguiculata (L) Walp) by isoenzyme electrophoresis(Postgraduate Institute of Agriculture, University of Peradeniya: Peradeniya, 1994) Eeswera, J. P; Peiris, C. NThe differences among cowpea (Vigna unguiculata (L) Walp) cultivars were identified using electrophoretically detected isozymic variability. The enzymes studied in the selected 10 cultivars of cowpea were Diaphorase (DIAP), Phospho Gluco Isomerase (PGI), 6Phospho Gluconate Dehydrogenase (6PGD), Phospho Gluco Mutase (PGM), Esterase (EST), Hexose Kinase (HK) and Glucose Oxalo Acetate Transaminase (GOT). Starch gel electrophoresis was used to analyze extracts prepared from young leaf tissues of seven day old seedlings of each cultivar grown under greenhouse conditions. Three enzymes GOT, HK, and PGM exhibited two patterns, while three different patterns were observed for EST and 6PGD. Phospho Gluco Isomerase showedfour different patterns, and DIAP appeared to be the most polymorphic with eight patterns. Distinct variety specific zymograms were observed for several enzymes. Unique combinations of isozymic variants of two enzyme systems assayed (DIAP and PGI) could differentiate all the culti*urs. Sufficient variability was present in cowpea cultivars to allow the use of isozyme electrophoresis as a method for cultivar identification. Therefore, ii could be used in variety identification to complement the morphological characters.Publication Open Access Plant growth flowering and fruit formation of tomato grown under protected culture(Postgraduate Institute of Agriculture, University of Peradeniya: Peradeniya, 1998) Weerakkody, W. A. P; Peiris, C. NProtected culture is a remedy for environmental problems of crop cultivation. However, seasonal weather changes adversely affect indoor grown plants. Therefore, this study was conducted to examine the affect of protected (indoor) culture and other improved technologies, often used in protected culture, on tomato (Lvcopersicon esculentum L.) grown with irrigation during the Maha season. Two indoor cultures together with improved technology and two outdoor (open-field) cultures with and without improved technology were used as treatments. Vegetative and reproductive growth of tomato were evaluated during the respective growth stages. Except at early vegetative growth, dry weather prevailed during the cropping season. Most of the vegetative growth parameters were not significantly different between the indoor and outdoor treatments. However, indoor culture showed significantly higher flowering and fruit formation. The shed house recorded the highest number of fruits per plant. Significantly higher vegetative growth was observed with the use of improved technologies, irrespective of the experimental conditions. Moreover, the improved technologies contributedfor greater number offlowers per plant but not for number of fruits. Indoor culture in combination with the improved technology assured greater vegetative growth, flowering and fruit formation of tomato when compared to outdoor culture under low rainy conditions that prevail during the Maha season. Except for fruitformation, comparative advantages of different indoor structures were not evident.Publication Open Access A gap analysis to measure service quality of university libraries through user perspectives: a case study at the University of Colombo(KDU Library, 2010) Somaratna, H. M. D. S. D; Peiris, C. N; Jayasundara, C. CUser expectations and perceptions are important measures of service quality in academic libraries and service quality is frequently defined in terms of reducing the gap between user expectations and the service provided. The assessment of service quality through user perspectives provides an important feedback for libraries. The aim of this research was to determine the gap between user desired service expectations and actual service perceptions of the University of Colombo Library System to provide a better service to satisfy their expectations. This study conducted as a user survey covered 614 users of the Colombo University Library system. A modified version of a SERVQUAL model was used to ascertain the views of library users about service level. They were asked to assess the actual service delivered by the library; to establish the importance of the service to them as users; and, to identify to what extent the service met their expectations. The largest service quality gap among all the attributes applied to the Colombo University Library System was “Access to electronic journals”. The author’s fervent hope is that this research would provide insights for further research in this field which in turn would eventually help decision makers to improve service quality in our academic libraries.