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Journal of the National Science Foundation of Sri Lanka
   [3 followers]  Follow    
  This is an Open Access Journal Open Access journal
     ISSN (Print) 1391-4588
     Published by Sri Lanka Journals Online Homepage  [45 journals]   [SJR: 0.144]   [H-I: 4]
  • A comparison of the physico-chemical and phytochemical parameters of
           glands/hairs of fruits and leaves of Mallotus philippensis (Lam.) Muell.
           Arg. grown in Sri Lanka

    • Authors: HGSP Hewageegana, LDAM Arawwawala, MHA Tissera, HAS Ariyawansa, I Dhammaratana
      Abstract: Medicinal oils prepared using glands/hairs of the fruits or leaves of Mallotus philippensis (Lam.) Muell. Arg., are prescribed for dermal problems. Although the glands/hairs of the fruits are mentioned, they are not freely available in the market. It is therefore useful to explore the possibility of using the leaves, which are freely available instead of glands/hairs for the preparation of medicated oils. The present study compares the physico-chemical properties and the phytochemical components in glands/hairs of the fruits and the leaves of M. philippensis. The extractive matter of glands/hairs of the fruits was significantly higher than that of the cold and hot ethanol extractive matter of the leaves. In addition, the amount of extractable matter observed in cold water extracts of glands/ hairs of the fruits and the leaves was very much less than that was found in other extracts. Total ash (10.9 %) and the acid insoluble ash (4.5 %) contents of the leaves were significantly higher than that of the glands/ hairs of the fruit. In addition, several important chemical constituents were present in the glands/hairs of the fruits and leaves of M. philippensis. These findings revealed the similarities of the physico-chemical and phytochemical parameters between glands/hairs of fruits and leaves of M. philippensis.
      DOI : J.Natn.Sci.Foundation Sri Lanka 2014 42 (3): 265-269
      PubDate: 2014-09-10
      Issue No: Vol. 42 (2014)
  • Design and fabrication of a novel hexagonal reconfigurable antenna with RF
           switches for mobile terminal

    • Authors: P Chawla, R Khanna
      Abstract: In this study a hexagonal reconfigurable fractal shaped antenna has been made using radio frequency microelectromechanical systems (RF MEMS) switches. The proposed design offers miniaturization of antenna by using hexagonal fractals as the patch of antenna. The fractal shape offers multiband resonance of antenna. Hexagonal fractal has been considered up to 2 iterations and the second iteration of antenna offers multiband resonance as required in modern-day wireless devices. The effect of photonic band gap (PBG) on the hexagonal antenna performance has also been studied. The reconfigurable nature of the proposed antenna is demonstrated by applying RF MEMS switches within the hexagonal patch after providing the appropriate slots. The proposed antenna is fabricated on FR4 laminate (d = 1.6 mm, εr = 4.7 and tanδ = 0.019) and analyzed in the frequency range 1.5 GHz to 7.5 GHz. The antenna is simulated using a high frequency structure simulator (HFSS) and verified by fabrication results. Both simulated and fabricated results show a considerable degree of agreement. The novelty in the design offers miniaturization of the size, multiband behaviour in comparison to antennas described in literature and the utility of such antenna in mobile RF front section.
      DOI : J.Natn.Sci.Foundation Sri Lanka 2014 42 (3): 257-263
      PubDate: 2014-09-10
      Issue No: Vol. 42 (2014)
  • Antioxidant activity and a new butanolide from the primitive endemic genus

    • Authors: Rukmal Ratnayake, Damith Perera, D Nedra Karunaratne, D Syril A Wijesundara, Gavin Carr, David E Williams, Raymond J Andersen, Veranja Karunaratne
      Abstract: The antioxidant activity of MeOH and dichloromethane extracts of the leaves and their alkaloid fractions of the three representative species of the endemic genus Hortonia were evaluated using DPPH radical scavenging bioassay. The results showed that the percentage yield of the basic compounds from all three species was very low. In general, the antioxidant activity of the leaf extracts and their acid washings was very low. It was also determined, contrary to what had been reported, that the alkaloid boldine was not found in detectable amounts in any of the acid washed fractions. Chemical investigations of the three species yielded a new butanolide, which was characterized by NMR and mass spectral data.
      DOI : J.Natn.Sci.Foundation Sri Lanka 2014 42 (3): 253-256
      PubDate: 2014-09-10
      Issue No: Vol. 42 (2014)
  • Analysis and mathematical modelling of possible inter-larval spread of the
           dengue virus

    • Authors: K Tennakone
      Abstract: The dengue virus continues its pathogenicity by horizontal transfer between humans and mosquitoes or vertical transfer through all metamorphic stages of infected female mosquitoes. A recent experiment has concluded the possibility of yet another mode of transmission, where the infected larvae in an aqueous habitat pass the virus to healthy ones. Although this mode of dengue virus transmission is not known to happen in nature, the virus adopting it as a survival strategy implicates a potential threat of more severe epidemics. A theoretical model constructed to study the spread of the virus suggests that when the larval population density exceeds a critical value the disease may quickly grow to epidemic proportions. The model also indicates that vertical transmission in the absence of human involvement is most unlikely to sustain the virus. Whereas in a densely larvae populated environment, inter-larval transmission could explosively generate infected mosquitoes without human mediation. The absolute necessity of eliminating mosquito breeding wet habitats and long term planning to avoid their creation is emphasized in light of this potential future threat. As evolution explores all the advantages and dengue virus evolves fast adaptively, virus resorting to inter-larval transmission should not be considered as an improbability.
      DOI : J.Natn.Sci.Foundation Sri Lanka 2014 42 (3): 247-251
      PubDate: 2014-09-10
      Issue No: Vol. 42 (2014)
  • Molecular detection and characterization of begomoviruses associated with
           cucurbitaceae vegetables in Sri Lanka

    • Authors: WMEK Bandaranayake, WART Wickramarachchi, HAM Wickramasinghe, RGAS Rajapakshe, DMKK Dissanayake
      Abstract: The family cucurbitaceae includes certain popular fruits and vegetables grown in various tropical and subtropical areas in the world. However, viral diseases are a major constraint causing heavy economical losses in cucurbits. Although a number of viral diseases have been reported in cucurbits in Sri Lanka, there are no reports of begomoviruses. A whitefly transmitted viral disease with severe leaf curl symptoms has been reported in bitter gourd from Sri Lanka (Momordica charantia), which was suspected to be due to a begomovirus. A PCR assay has been conducted using universal primers (Deng 540 and Deng 541) specific for begomoviruses to detect the viruses associated with various cucurbits showing viral symptoms. The begomovirus associated with bitter gourd was characterized by nucleotide sequence analysis. Infection by begomoviruses in bitter gourd, ridge gourd (Luffa acutangula), pumpkin (Cucurbita maxima), cucumber (Cucumis sativus) and snake gourd (Trichosanthes cucumerina) plants, which showed symptoms of upward leaf curl, leaf mosaic, shortening internodes, mottling, stunting, rosetting, puckering, reduced leaf lamina, fruit malformation and flatterning of tender stems were confirmed by consistent amplification of core coat protein CP gene fragment of 520 bp. No amplification was observed with healthy cucurbit samples. The sequence comparison and phylogenetic analysis of the coat protein gene of begomovirus in bitter gourd (Begomo-Bitter Gourd-Sri Lanka Virus) showed 97 % nucleotide identity and a close genetic relationship with the Tomato leaf curl New Delhi virus in bitter gourd found in Pakistan (ToLCNDV-BG).
      DOI : J.Natn.Sci.Foundation Sri Lanka 2014 42 (3): 239-245
      PubDate: 2014-09-10
      Issue No: Vol. 42 (2014)
  • Characterization of bio-physical features in Thalawila fishing ground,
           North-western coast of Sri Lanka

    • Authors: HB Jayasiri, K Arulananthan, SUP Jinadasa
      Abstract: Fish aggregation is area specific and strongly links with oceanographic processes and parameters. The sea off Thalawila in the North-western region of Sri Lanka is a major fishing ground particularly for the tuna longline fishery. To study the monsoon response on fishing, environmental data on temperature, conductivity, depth and chlorophyll profiles along with plankton sampling were collected at seven selected locations during the first inter-monsoon and the Northeast monsoon in 2007. The depth of the thermocline was 80 − 90 m during the inter-monsoon, and 40 − 60 m during the Northeast monsoon. The observations indicated that the depth of the chlorophyll-a maximum varied from 20 − 80 m. The deepest depth of chlorophyll maxima was found in April. However, there was a broader peak of chlorophyll varying within the depth range of 20 − 80 m in January and March. The values of mean phytoplankton and zooplankton abundances of the area were 3273 ± 771 and 55.36 ± 9.82 indi. L-1, respectively. The chlorophyll-a concentration and the zooplankton density varied as a function of time, but the spatial variability was less significant. The relative compositions of phytoplankton revealed that diatoms dominated with 91 % of the total population followed by 8 % dinoflagellate contribution. The zooplankton analysis indicated the dominance of crustacean larvae comprising about 48.4 % with copepods of about 37.04 %. The present analysis indicated that chlorophyll significantly correlated with the phytoplankton and zooplankton density (p < 0.01). The findings suggest that thermal structure of the water column and food availability are likely to determine the aggregation of fish off the North-western coast of Sri Lanka.
      DOI : J.Natn.Sci.Foundation Sri Lanka 2014 42 (3): 229-238
      PubDate: 2014-09-10
      Issue No: Vol. 42 (2014)
  • Surfactant-assisted synthesis of pure calcium carbonate nanoparticles from
           Sri Lankan dolomite

    • Authors: MMMGPG Mantilaka, WPSL Wijesinghe, HMTGA Pitawala, RMG Rajapakse, DGGP Karunaratne
      Abstract: Sri Lanka is rich in extensive deposits of dolomitic marbles with large quantities, which have not yet been exploited on an industrial-scale to produce value-added products such as precipitated calcium carbonate (PCC) nanoparticles. PCC is used extensively and is imported by Sri Lankan industries for application as a filler and extender. Hence, this work attempts to examine Sri Lankan impure dolomitic marbles as a source for the synthesis of pure PCC nanoparticles, so as to fulfill the current industrial demand and to add value to the cheap and mundane marbles. As reported in this paper, the calcium (Ca) components of the marbles can be extracted from impurities by preparing solutions of saturated calcium hydroxide, calcium citrate, Ca2+-ethylenediaminetetraacetic acid complexes and calcium sucrate, separately from dolomite. PCC nanoparticles are then synthesized by adding sodium carbonate to each calcium extract. The results shows that the best extract to synthesize PCC nanoparticles with high yield and purity is calcium sucrate. Here, calcium sucrate has been used for surfactant assisted hydrothermal synthesis of PCC nanoparticles with particle sizes ranging from 38.9 − 51.6 nm, which is a novel effort. This method could be applied to manufacture PCC nanoparticles on an industrial-scale.
      DOI : J.Natn.Sci.Foundation Sri Lanka 2014 42 (3): 221-228
      PubDate: 2014-09-10
      Issue No: Vol. 42 (2014)
  • Oligomeric proanthocyanidin fractions from fresh tea leaves and their
           antibacterial activity against Staphylococcus aureus

    • Authors: N Savitri Kumar, BM Ratnayake Bandara, Sujeewa K Hettihewa, Gehan J Panagoda
      Abstract: Purification of the proanthocyanidin (PA) extract of fresh tea [Camellia sinensis (L.) Kuntze] leaves by Sephadex LH-20 column chromatography followed by high-speed counter-current chromatography (HSCCC) using the two phase solvent system hexane-ethyl acetate-methanol-water (1:5:1:5) furnished three PA fractions PA1- PA3. The electro-spray ionization mass spectrometry (ESI-MS) of the PA fractions indicated the presence of oligomeric PAs in all three PA fractions. Antibacterial activity against Staphylococcus aureus and their minimum inhibitory concentration (MIC) values were determined using the agar well diffusion assay and the agar dilution method, respectively. The antibacterial activity was observed for the selected PA fractions with MIC values in the range 512 − 1024 μg/mL against methicillin-resistant S. aureus (MRSA, 12 strains), methicillin-susceptible S. aureus (MSSA, 1 strain) and two standard strains of S. aureus, NCTC 6571 and ATCC 25923S. This is the first report of antibacterial activity displayed by tetrameric A-type PAs in the extracts of fresh tea leaves.
      DOI : J.Natn.Sci.Foundation Sri Lanka 2014 42 (3): 215-220
      PubDate: 2014-09-10
      Issue No: Vol. 42 (2014)
  • Effect of exogenous pH on development and growth of Colletotrichum musae

    • Authors: DM De Costa, AAG Chandima
      Abstract: In the present study, the relationship between the observed inter-cultivar variation of anthracnose development in banana by Colletotrichum musae and fruit peel pH was investigated. The results of a survey showed that anthracnose does not develop on Mondan (ABB), a cooking-type cultivar. In contrast, the highest susceptibility to anthracnose was reported by the dessert cultivars Anamalu and Embon (AAA). Variations of the pH of fruit peel exudates (FPE) of different banana cultivars were monitored during the ripening stages. The effects of FPE, collected from different banana cultivars at two maturity stages, on germ tube formation and elongation and appressoria development of C. musae were also determined. Furthermore, the effects of culture medium pH on the growth of C. musae, anthracnose development and the expression of a virulence-related gene, pelB were determined. With ripening the pH of FPE and fruit pulp decreased. The highest pH of FPE was shown by cultivars Seenikehel, Alukehel and Mondan with pH values greater than 6.0 at mature-unripe stage. At the ripe stage, pulp of all cultivars had pH values less than 4.5 with the lowest being 3.9 in Embul. When grown in culture media at a pH range from 4.0 – 8.0, the highest mycelial growth of C. musae was observed at 4.5, indicating that an exogenous pH of 4.5 can favour colonization by C. musae. The expression of pelB gene was detected by RT-PCR only in C. musae grown in a culture medium having a pH of 4.5. In addition, soluble solid content of the fruit peel was quantified as a possible factor responsible for the variation in anthracnose development among different banana cultivars, and its effects on germ tube formation, elongation and appressoria formation are discussed.
      DOI : J.Natn.Sci.Foundation Sri Lanka 2014 42 (3): 203-214
      PubDate: 2014-09-10
      Issue No: Vol. 42 (2014)
  • RTOS based embedded controller implementation of a bilateral control

    • Authors: AM Harsha S Abeykoon, M Branesh Pillai
      Abstract: Bilateral tele-operation involves realization of the law of action and reaction between the human and the remote environment. In this research, an embedded system based bilateral control was developed on a microcontroller based motor driver platform. Bilateral tele-operation needs real-time representation of the forces and positions. This challenge was accomplished by incorporating a real-time operating system (RTOS) with a resource limited microcontroller. Sensorless torque detection technique was used to find the external torque while disturbance observer was used as a disturbance rejection tool and also to improve the system’s robustness. When the motion controller was implemented on a microcontroller, 0 - 30 Hz frequency of force bandwidth could be achieved. In an ideal bilateral control, force/position errors should be zero. The experimental results in contact motion showed a force error less than 4 % and a position error less than 6 %, which validates the proposal. This was a significant achievement as the bilateral controllers have never been successfully implemented using a microcontroller.
      DOI : J.Natn.Sci.Foundation Sri Lanka 2014 42 (3): 191-202
      PubDate: 2014-09-10
      Issue No: Vol. 42 (2014)
  • Electron spin resonance spectroscopic measurement of antioxidant activity
           of organic solvent extracts derived from the methanolic extracts of Sri
           Lankan thebu leaves (Costus speciosus)

    • Authors: Kalpa W Samarakoon, HH Chaminda Lakmal, Seo Young Kim, You-Jin Jeon
      Abstract: In this study, the antioxidant effects of different solvent soluble fractions derived from the methanolic extracts of the Sri Lankan thebu plant (Costus speciosus) leaves were assessed. For the antioxidant activity of the extracts, 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl and alkyl radical scavenging potentiality were measured using electron spin resonance (ESR) spectroscopy compared to the standard antioxidant ascorbic acid. Among the extracts, ethyl acetate fraction (T-EA) indicated the strongest scavenging activity against hydroxyl and alkyl radicals with the IC50 values 0.046 ± 0.002 and 0.055 ± 0.004 mg mL-1, respectively. The aqueous fraction (T-WE) indicated the highest DPPH radical scavenging activity (IC50 value 0.110 ± 0.01 mg mL-1). The total phenolic content in thebu extracts was the highest in T-EA fraction with 6.57 %. Moreover, both T-EA and T-WE fractions did not show any significant cytotoxic effect against vero cells in vitro assays. These results indicated the profound antioxidant effects of the Sri Lankan thebu leaf extracts for the first time. Isolation of antioxidative compounds from T-EA and T-WE fractions and in vitro antioxidant effects can be considered in further studies.
      DOI : J.Natn.Sci.Foundation Sri Lanka 2014 42 (3): 183-190
      PubDate: 2014-09-10
      Issue No: Vol. 42 (2014)
  • El Nino - A short term signal of a long term and a large scale climate

    • Authors: WL Sumathipala
      DOI : Sri Lanka 2014 42 (3): 173-174  
      PubDate: 2014-09-10
      Issue No: Vol. 42 (2014)
  • Preliminary investigation for the identification of Sri Lankan Cinnamomum
           species using randomly amplified polymorphic DNA (RAPD) and sequence
           related amplified polymorphic (SRAP) markers

    • Authors: PD Abeysinghe, NGCD Samarajeewa, G Li, KGG Wijesinghe
      Abstract: Cinnamon is one of the important minor export crops in Sri Lanka. Cinnamomum verum Presl is known as true cinnamon and seven other wild Cinnamomum spp. such as C. dubium Nees, C. citriodorum Thw., C. capparu– coronde Blume, C. litseaefolium Thw., C. ovalifolium Weight, C. rivulorum Kostermans and C. sinharajaense Kostermans are native to Sri Lanka. The identification of Cinnamomum species is still based on morphological characters, which are influenced by environmental factors. Therefore, molecular markers such as randomly amplified polymorphic DNA (RAPD) and sequence related amplified polymorphism (SRAP) were employed in order to find a more reliable approach to identify Cinnamomum species correctly. Using RAPD and SRAP techniques, it was possible to detect the polymorphism as well as to identify the Cinnamomum species. Fourteen RAPD primers and 20 sets of SRAP primer combinations gave amplification products. However, one set of SRAP primer combinations produced more markers for Cinnamomum species than the RAPD markers. Amplification products from both techniques could be categorized as genus specific, species specific and intra-species specific markers. Both polymerase chain reaction (PCR) based techniques employed in this study can be used to identify the species, to estimate the genetic diversity of Cinnamomum spp. and to detect polymorphism, which could be used to screen the accessions of germplasm collected at the Department of Export Agriculture, Sri Lanka.
      DOI : Sri Lanka 2014 42 (3): 175-182
      PubDate: 2014-09-10
      Issue No: Vol. 42 (2014)
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