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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  [40 journals]   [SJR: 0.144]   [H-I: 4]
  • Author Index Vol 41-2013
    • Authors: The Editor
      PubDate: 2013-12-30
      Issue No: Vol. 41 (2013)
       
  • Subject Index Vol 41-2013
    • Authors: The Editor
      PubDate: 2013-12-30
      Issue No: Vol. 41 (2013)
       
  • Natural rubber latex-clay nanocomposite: use of montmorillonite clay as an
           alternative for conventional CaCO3
    • Authors: A Amarasiri, UN Ratnayake, UK De Silva, S Walpalage, S Siriwardene
      Abstract: Natural rubber (NR) latex-clay nanocomposite (NRLCN) synthesized with montmorillonite (MMT) clay aqueous dispersion was evaluated for reinforcement and barrier properties. The physio-mechanical properties of the NRLCN were compared with the conventional NR latex composites containing CaCO3. The NRLCN structure was characterized with X-ray diffraction and scanning electron microscope techniques. The X-ray diffraction data showed that, with a lower concentration of clay, a highly exfoliated clay structure was achieved whilst the clay aggregation gradually resulted in a higher concentration of clay. The crosslink density as computed based on the solvent absorption data of the latex nanocomposite films was increased with the increase of clay concentration. As a result of nanoscale dispersion of the montmorillonite clay and higher crosslink density of the latex nanocomposite films, the resistance to permeation of small molecules through the NRLCN was significantly enhanced in comparison to conventional NR latex-CaCO3 composites. Solid state mechanical properties of NRLCNs showed a significant reinforcement effect of dispersed clay platelets but without significantly reducing the elastic properties. The higher mechanical properties and improved barrier resistance indicated that NR latex nanocomposites containing montmorillonite clay is a potential replacement for conventional NR latex composites containing CaCO3. J.Natn.Sci.Foundation Sri Lanka 2013 41 (4): 293-302
      DOI : http://dx.doi.org/10.4038/jnsfsr.v41i4.6258
      PubDate: 2013-12-13
      Issue No: Vol. 41 (2013)
       
  • Storage and germination treatments for seeds of an ornamentally important
           palm, Livistona rotundifolia (Lam.) Mart.
    • Authors: BLG Sanjeewani, KMGG Jayasuriya, MTR Fernando, JW Damunupola
      Abstract: Livistona rotundifolia (Lam.) Mart. is an ornamentally important plant in Sri Lanka with a high demand for both cut foliage and pot plant production for the foreign market. Propagation through seeds, poor germination and the storage of seeds are the main constraints in L. rotundifolia cultivation. During the current study, seed germination and storage behaviour of L. rotundifolia have been investigated to identify the causes for its poor germination and poor storability. The moisture content of seeds was determined using the oven-dry method. Germination of the seeds was studied under light/dark and dark conditions and the embryo : seed ratio was determined in fresh seeds and in seeds soon after the radicle emergence. The effect of storage at eight different storage conditions was evaluated. The seeds had a moisture content of 36.8 % suggesting that they are recalcitrant. Recalcitrancy of seeds is further supported where none of the seeds germinated when they were stored at −2 oC. Freshly collected seeds germinated only in dark conditions (58 %). Even in dark conditions, the seeds took 2 months to complete germination. Although seeds had a low embryo : seed ratio, it remained unchanged during germination. Thus, the dormancy of seeds can be categorized as the non-deep physiological dormancy. This is the first record of a species producing seeds with no morphological dormancy in Arecaceae. The seeds stored in polythene bags with coir dust at 4 − 8 oC showed the highest survival (97 %) and thus, this treatment can be recommended to store L. rotundifolia seeds for a minimum of 5 months.J.Natn.Sci.Foundation Sri Lanka 2013 41 (4): 273-277
      DOI : http://dx.doi.org/10.4038/jnsfsr.v41i4.6257
      PubDate: 2013-12-13
      Issue No: Vol. 41 (2013)
       
  • A remote sensing and GIS based study in assessment of the degradation risk
           of the Kolonnawa marsh
    • Authors: YMP Samarasinghe, NDK Dayawansa
      Abstract: A majority of the Sri Lankan wetlands is under threat of degradation mainly due to urbanization, population pressure and industrialization. This study was conducted to detect the changes and to assess and map the degradation risk of the Kolonnawa marsh located in the Western Province of Sri Lanka by analyzing the data collected through field surveys, remote sensing and GIS techniques. A questionnaire survey was conducted within 11 Grama Niladhari (GN) Divisions around the marsh to obtain information on household characteristics, interactions with the marsh, awareness on marsh degradation and marsh conservation. According to the temporal change assessment performed with Landsat TM (1992), Landsat ETM+ (2002) satellite images, 32 % of the marsh area has been reduced in 1992 - 2002 period. According to Worldview 2 image, the total marsh area including the associated waterways in 2010 was 144.56 ha. A risk index was formulated considering the risk factors prevailing in the study area. Risk mapping, which was carried out based on the risk index resulted in three risk classes; moderate, high and very high. Mapping based on the risk index was helpful to identify the severity of the degradation risk of the marsh at GN Division level. The study identified that all surrounding GN Divisions pose risk on degradation of the marsh while the highest impact was reported from the Obesekarapura GN Division. The risk matrix was identified as an important tool in prioritizing the areas for conservation.J.Natn.Sci.Foundation Sri Lanka 2013 41 (4): 327-335
      DOI : http://dx.doi.org/10.4038/jnsfsr.v41i4.6256
      PubDate: 2013-12-13
      Issue No: Vol. 41 (2013)
       
  • Towards a green economy in Sri Lanka: A forestry perspective
    • Authors: Nimal Gunatilleke
      Abstract:
      DOI : http://dx.doi.org/10.4038/jnsfsr.v41i4.6255 J.Natn.Sci.Foundation Sri Lanka 2013 41 (4): 271-272
      PubDate: 2013-12-12
      Issue No: Vol. 41 (2013)
       
  • Use of biochemical compounds in tea germplasm characterization and its
           implications in tea breeding in Sri Lanka
    • Authors: JD Kottawa-Arachchi, MTK Gunasekare, MAB Ranatunga, PAN Punyasiri, L Jayasinghe
      Abstract: Thirty five tea germplasm accessions selected to represent the germpalsm collection of Sri Lanka was used for biochemical characterization based on the biochemical compounds present in the fresh tea leaf. Rate of fermentation, crude fibre content, total polyphenols, total catechins, chlorophyll-a, chlorophyll-b and total carotenoids were analysed. Principal component analysis (PCA) using 7 biochemical parameters and clustering on first three principal components accounted for 87 % of the total variation and delineated the 35 accessions into 4 clusters. Biochemical parameters such as fermentation rate, total polyphenols, total catechins and plant pigments in green leaf were important in explaining the biochemical variation. The selected 35 accessions could also be categorized into 4 groups based on the fermentation rate. Estate selections (PK2, N2, DUN7, S106, DT1, TC9, WT26 and NAY3) and some introductions (TRI777, INTRI6 and VHMOR) recorded the highest total polyphenols and catechin content. Besides, ASM4/10, TRI2016, TRI2025 and TRI2043 showed the highest content of chlorophylls and total carotenoids. The significant variation of the selected biochemical compounds detected in the present study indicated the high genetic diversity of tea germplasm in Sri Lanka. Results suggests that accessions PLLG2, VHMOR, DUN7 and WT26 possess unique characteristics such as rapid fermentation, high amount of polyphenols and catechins, and these could be used as potential parents for future tea breeding programmes after analyzing other complementary traits. The present study provides useful guidelines on the use of fresh leaf biochemical parameters such as the rate of fermentation, total polyphenols, total catechins, chlorophylls and carotenoid content in characterizing the Sri Lankan tea germplasm.J.Natn.Sci.Foundation Sri Lanka 2013 41 (4): 309-318
      DOI : http://dx.doi.org/10.4038/jnsfsr.v41i4.6252
      PubDate: 2013-12-12
      Issue No: Vol. 41 (2013)
       
  • Spectrophotometric and pH-metric studies on Pb(II), Cd(II), Al(III) and
           Cu(II) complexes of paracetamol and ascorbic acid
    • Authors: AMDS Chandrathilaka, OA Ileperuma, CV Hettiarachchi
      Abstract: Spectrophotometric and pH-metric studies of the aqueous binary and mixed ligand complexes of Pb(II), Cd(II), Al(III) and Cu(II) were carried out with ascorbic acid and paracetamol. The study was conducted at an ionic strength of 0.15 mol dm-3 and a temperature of 37.0 ± 0.2 oC. The protonation constants of the free ligands and the stability constants of the binary and mixed ligand complexes were determined using pH titration data. Proton dissociation of free ligands and complex formation were also qualitatively confirmed with UV data. The stabilities of mixed ligand complexes were quantitatively compared with those of the corresponding single ligand complexes in terms of Δlog K. Aluminium formed the most stable binary complex; Al (paracetamol)2, with a high overall stability constant (log β2 = 16.74). The stable mixed ligand complexes; Pb (ascorbic acid) (paracetamol), Cd (ascorbic acid)(paracetamol) and Cu (ascorbic acid) (paracetamol) were observed with positive Δlog K values showing the ability of using them in less harmful chelation therapy of these metals. Further, the results revealed that the bioavailability of both ligands will be lower for a metal intoxicated person.J.Natn.Sci.Foundation Sri Lanka 2013 41 (4): 337-344
      DOI : http://dx.doi.org/10.4038/jnsfsr.v41i4.6253
      PubDate: 2013-12-12
      Issue No: Vol. 41 (2013)
       
  • Potent bioactivities of the endemic Annonaceae heightens its dire
           conservation status
    • Authors: Aruna Weerasinghe, Shanmugam Puvenendran, Anura Wickramasinghe, D Nedra Karunaratne, Siril Wijesundara, Veranja Karunaratne
      Abstract: Sri Lanka records 17 endemic species of the Annonaceae family. Worldwide, the Annonaceae are known to possess compounds with pharmaceutically important properties such as anticancer and insecticidal actions. In an attempt to investigate the mosquito larvicidal and antioxidant activities of the endemic Annonaceae plants, twelve plant species were collected. Of the 71 extracts investigated from various plant parts, five plants showed significant larvicidal activity with the CH2Cl2 extracts of the leaves of G. hookeri and G. gardneri (LC50 at 48 h = 0.4 and 0.3 ppm, respectively) exhibiting potency compared to the known larvicide (4S)-4- methyl-2-(11-dodecynyl)-2-butenolide (LC50=0.3 ppm). Compared to the percent radical scavenging activity of the standard dl-α tocopherol (55.84), the MeOH extracts of the stem of A. hortensis (56.30), the leaves of U. semecarpifolia (57.33), and the seeds of X. nigricans (62.06) showed very promising activity. Significantly, it is recorded that two of the Sri Lankan endemic Annonaceae plants are extinct (P. moonii and A. hortensis) and the rest, except for U. sphenocarpa, are critically endangered, endangered, vulnerable or near threatened. These grim statistics highlight not only the urgency and the importance of biodiversity conservation of the endemic Annonaceae of Sri Lanka but also of investigating the plants for new phamacophores.J.Natn.Sci.Foundation Sri Lanka 2013 41 (4): 345-350
      DOI : http://dx.doi.org/10.4038/jnsfsr.v41i4.6251
      PubDate: 2013-12-12
      Issue No: Vol. 41 (2013)
       
  • Fingerprinting diesel and petrol fuels for adulteration in Sri Lanka
    • Authors: DR Kulathunga, KRR Mahanama
      Abstract: Adulteration of petrol (gasoline) and diesel using petrochemical based products has often been reported in developing countries. This leads to the degradation of engine performances and fugitive emissions. Having similar chemical properties, the fuel and the adulterant cannot be distinguished easily leading to complications in identification and quantification of the adulterants. In this investigation, a synchronous fluorimetric analysis method was modified targeting to obtain the fingerprints for these fuels based on their polycyclic aromatic hydrocarbon (PAH) content. In a synchronous fluorescence scan, both the excitation and emission wavelengths are scanned keeping the wavelength difference at a fixed value. PAHs are a group of compounds with fused benzene ring systems, which are naturally present and/or formed during fuel processing that exhibit significant differences in their synchronous fluorescence scans. Simulated adulterated samples of petrol or diesel with kerosene, diluted in hexane, were prepared from the fuels collected from the petroleum refinery. These simulated fuel samples showed linear variations of the synchronous emission intensity with the level of kerosene in the fuel at specific wavelengths. This relation was utilized to investigate the level of adulteration for petrol and diesel available at different petrol stations. Diesel adulteration was found to be in the range of 0 to 35 % while petrol adulteration was found to be in the range of 0 to 48 % in Colombo and its suburbs.J.Natn.Sci.Foundation Sri Lanka 2013 41 (4): 287-292
      DOI : http://dx.doi.org/10.4038/jnsfsr.v41i4.6247
      PubDate: 2013-12-11
      Issue No: Vol. 41 (2013)
       
  • Radioactivity levels in beach sand from the West Coast of Sri Lanka
    • Authors: P Mahawatte, KNR Fernando
      Abstract: Concentration of primordial radionuclides in 48 sand samples collected from the coastal strip from Uswetakeyyawa to Chillaw in the West Coast of Sri Lanka was measured using a high purity germanium (HPGe) detector. The measured activity concentrations of 232Th ranged from 14 ± 3 to 6257 ± 38 Bq kg-1. The maximum concentrations of 238U and 40K measured were 1243 ± 15 and 647 ± 37 Bq kg- 1, respectively and the minimum were below the detection limits. The detection limits of 238U, 232Th and 40K were 1.70, 2.37 and 10.41 Bq kg -1, respectively. The calculated external annual effective dose rate at one meter aboveground ranged from 5 - 4567 nGyh-1. More than 50 % of the samples analysed showed radium equivalent activity concentrations above the limit 370 Bq kg-1, which is the value recommended for the safe use of building materials for dwellings. The same 48 samples were parallely analysed using NaI (Tl) scintillation spectrometry. For 238U and 232Th the mean ratios of the values obtained by the two methods were 1.0148 and 1.0018, respectively. The findings of this study shows that scintillation spectrometry provides a cost effective method to measure U and Th in radioactive beach sand.J.Natn.Sci.Foundation Sri Lanka 2013 41(4): 279-285
      DOI : http://dx.doi.org/10.4038/jnsfsr.v41i4.6249
      PubDate: 2013-12-11
      Issue No: Vol. 41 (2013)
       
  • X-ray crystal structure analysis of 4,7-dioxononanoic acid
    • Authors: AM Abeysekera, C Padumadasa, SMVD Mala
      Abstract: The structure of 4,7- dioxononanoic acid previously assigned on the basis of its NMR spectra, was confirmed by X-ray crystallography. The compound exhibits only one sharp peak in its solid state IR spectrum at 1685 cm-1 for its three carbonyl groups. A plausible explanation for this anomaly is provided by X-ray crystallography on the basis of crystal packing and dipole-dipole interactions in aligned arrays of carbonyl groups. This alignment is found in the carboxylic acid group as well, so that the hydrogen bonded interactions of the two carboxylic acid groups found normally in the "dimeric" structures of carboxylic acids in the solid state are not present in the title compound. J.Natn.Sci.Foundation Sri Lanka 2013 41(4): 303-307
      DOI : http://dx.doi.org/10.4038/jnsfsr.v41i4.6248
      PubDate: 2013-12-11
      Issue No: Vol. 41 (2013)
       
  • Preliminary survey of the distribution of four potentially zoonotic
           parasite species among primates in Sri Lanka
    • Authors: MA Huffman, CAD Nahallage, H Hasegawa, S Ekanayake, LGDD De Silva, IRK Athauda
      Abstract: The occurrence of four parasitic species of zoonotic potential, Entamoeba coli, Entamoeba histolytica / dispar, Trichuris sp. and hookworm was investigated in the toque macaque, grey langur and the purple-faced langur at 32 sites across Sri Lanka. The study was carried out during the rainy season months of February - March in both 2007 and in 2009 and in December of 2010. 93 faecal samples were collected from 49 monkey troops at representative locations in altitudinal /climatic zones across the country where toque macaques (58 samples), grey langurs (21 samples) and purple-faced langurs (14 samples) naturally occur. Overall, the most common parasitic species found in all three primates were Trichuris sp. (28 %) and E. coli (25 %). Notably, hookworms were present in 23 % of the grey langur samples and 33 % of the toque macaque samples but absent in the purple-faced langur samples collected. Statistically significant variability in the prevalence levels across altitudinal/climatic zones was noted for toque macaques. Overall, group prevalence values in toque macaques decreased with increasing altitude; the highest values were found in the intermediate to arid lowland zones, and were lowest in the upland wet zone. Only Trichuris sp. and hookworm were found (13 %, 7 %, respectively) in the highland/ wet zone. Molecular analysis will be necessary to genetically type the parasite species before drawing firm conclusions about the status of zoonotic transmission between humans and non-human primates in the country. However this study highlights the need to systematically survey the human parasite population in areas where primates are commonly found to harbour these parasite species.J.Natn.Sci.Foundation Sri Lanka 2013 41(4):319-326
      DOI : http://dx.doi.org/10.4038/jnsfsr.v41i4.6246
      PubDate: 2013-12-11
      Issue No: Vol. 41 (2013)
       
 
 
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